The stock market has a strange way of making us regret things that, in the long run, may not matter very much.
You didn’t buy the stock that doubled in a month. You kept some cash while the market continued making new highs. You bought a fundamentally good company just before a 20% correction. Or perhaps you sold a winner at ₹1,000 and watched helplessly as it climbed to ₹1,500.
These things hurt. Sometimes they hurt a lot.
But here’s the important part: your portfolio can forgive them.
Another multibagger will eventually come along. Markets will correct again. A good business can recover from a temporary fall. And nobody consistently sells at the exact top.
There are, however, some investing mistakes that are far less forgiving. They can permanently destroy capital, force you to make decisions at the worst possible time, or leave your money trapped in a deteriorating business for years.
Here are five mistakes I believe investors should be particularly careful about.
1. Borrowing Money to Invest
Borrowing money to invest can look incredibly attractive during a bull market.
Imagine borrowing ₹10 lakh at an interest rate of 10% and investing it in stocks that subsequently rise 30%. On paper, the mathematics looks wonderful. Your investment gains ₹3 lakh while the annual interest cost is around ₹1 lakh.
When markets keep rising, leverage can make an investor feel exceptionally smart.
The real test begins when the market falls.
Suppose your ₹10 lakh portfolio drops to ₹7 lakh and remains there for the next two years. Your stocks may eventually recover, but the lender isn’t going to wait patiently for the next bull market. Interest payments continue regardless of what the Sensex or Nifty is doing.
That creates a dangerous situation.
You may have identified excellent companies and still be forced to sell them near the bottom simply because you need money to service the loan.
An investor using his own surplus money usually has one enormous advantage during a market crash: the ability to wait.
Leverage can take that advantage away.
The biggest danger of borrowing to invest isn’t simply that stocks can fall. It is that your financial obligations can force you to sell before your investment thesis has had enough time to work.
2. Buying a Stock Just Because It Has Fallen 50%
Few things attract investors faster than a stock trading at half its previous price.
A company that was trading at ₹500 six months ago is suddenly available at ₹250. The immediate reaction is often:
“How much lower can it possibly go?”
Unfortunately, quite a lot.
A 50% decline doesn’t automatically make a stock cheap because price and value are two different things.
Suppose a company was earning ₹10 per share when its stock traded at ₹500. The market was valuing it at 50 times earnings.
Now imagine its earnings fall to ₹5 because margins have collapsed and competition has intensified. At ₹250, the stock is still trading at 50 times its reduced earnings.
The share price has halved, but the valuation hasn’t become cheaper at all.
This is why investors need to understand why a stock has fallen.
Sometimes the market genuinely overreacts. A temporary earnings disappointment, an industry slowdown or short-term regulatory uncertainty can push a fundamentally strong company well below its intrinsic value. Those situations can create excellent opportunities.
But sometimes the market is signalling something more serious: rising debt, deteriorating cash flows, loss of market share, governance concerns or a structural change in the business.
Don’t ask only:
“How much has the stock fallen?”
Ask:
“Has only the price fallen, or has the underlying business deteriorated too?”
That distinction can separate a bargain from a value trap.
3. Letting One Stock Become Half Your Portfolio
I believe investors should take meaningful positions in their best ideas.
There is little point in spending weeks researching a company, developing strong conviction and then allocating only 1% of your portfolio to it. Even if the stock doubles, the impact on your overall wealth will be limited.
At the same time, conviction shouldn’t become overconfidence.
Allowing a single company to represent 40–50% of your entire equity portfolio means that one unexpected event can dramatically alter your financial position.
And there are always things investors cannot predict.
A trusted promoter can suddenly face a governance controversy. A government regulation can change the economics of an industry. A key customer can leave. A new competitor can disrupt pricing. An acquisition can fail. Technology can make an existing product less relevant.
You can read every annual report, listen to every conference call and understand the industry exceptionally well—and still encounter something you never anticipated.
For my own style of investing, around 25–30 carefully selected stocks provides a comfortable balance between diversification and meaningful position sizes. Other investors may prefer a more concentrated portfolio depending on their knowledge, risk tolerance and ability to track businesses closely.
The exact number isn’t the important part.
The principle is.
Research reduces uncertainty. Diversification protects you from the uncertainty that research cannot eliminate.
4. Celebrating Sales Growth Without Checking Cash Flow
A company announcing 40% revenue growth immediately gets attention.
Sales are rising rapidly. Profits may also be increasing. Management talks enthusiastically about expansion, new customers and future opportunities.
Everything looks great.
But before getting excited, I like to ask another question:
Where is the cash?
Imagine a company whose revenue rises from ₹500 crore to ₹700 crore—a healthy 40% increase.
Now suppose its trade receivables rise from ₹100 crore to ₹220 crore during the same period.
That deserves investigation.
The company may genuinely be growing quickly and offering longer credit periods to large customers. It may be building inventory ahead of future demand. Rapid expansion can naturally consume working capital.
None of these things automatically indicate a problem.
But if receivables, inventory and borrowings consistently grow faster than sales while operating cash flow remains weak, investors should look deeper.
Accounting revenue is recorded when a sale is recognised. Cash arrives only when the customer actually pays.
Over several years, a healthy business should generally demonstrate a reasonable relationship between reported profits and cash generation, although the pattern can vary considerably by industry and stage of growth.
That’s why looking only at the profit and loss statement can give an incomplete picture.
Revenue shows how fast the business is growing. Cash flow helps show the quality of that growth.
5. Waiting for Your Buying Price to Come Back
This is perhaps the most human mistake on the list.
You buy a stock at ₹500.
It falls to ₹400.
Then ₹350.
Eventually it reaches ₹250.
You have gradually stopped thinking about the company’s future prospects. Instead, one number dominates your mind:
₹500.
You tell yourself:
“I’ll sell as soon as it comes back to my buying price.”
But ₹500 has no special meaning to the market.
The company doesn’t know where you bought it. Other investors don’t care. Future earnings aren’t influenced by your purchase price.
₹500 matters only because you paid ₹500.
There is a simple mental exercise that can help in such situations.
Imagine that you don’t own the stock.
Someone gives you its current market price, financial statements, valuation and business outlook today and asks:
“Would you buy this company now?”
If the answer is yes, continuing to hold may make perfect sense.
But if your answer is an emphatic no, ask yourself why you are still holding it.
Sometimes investors remain trapped in weak businesses for years simply because booking a loss feels like admitting a mistake.
Meanwhile, better companies continue compounding elsewhere.
This is where opportunity cost becomes important. A stock doesn’t need to fall another 50% to hurt your portfolio. If it goes nowhere for five years while a better business compounds steadily, the damage is still significant.
Your buying price belongs to the past. Investing decisions should be based on what you expect from the business from today onward.
Some Mistakes Hurt. Others Can Set You Back for Years
You are going to make mistakes in the stock market.
Every investor does.
You will miss multibaggers. You will occasionally buy before a correction. You will hold too much cash during a rally. And you will inevitably sell some wonderful companies earlier than you should have.
Don’t spend too much emotional energy worrying about those mistakes.
The market will give you more opportunities.
What deserves greater attention are mistakes that can permanently damage your capital or take away your ability to wait for the next opportunity.
Borrowing money to invest can force you to sell at the worst possible time.
Buying merely because a stock has fallen can turn a correction into a value trap.
Excessive concentration can allow one unexpected event to damage your entire portfolio.
Ignoring cash flow can make poor-quality growth look much better than it really is.
And anchoring yourself to your purchase price can keep your money trapped in a broken investment for years.
Missing one multibagger can be painful.
But there will always be another stock, another correction and another opportunity.
Recovering from excessive leverage, reckless concentration or years spent waiting for a broken business to recover is far more difficult.
The goal of investing isn’t to make every decision perfectly.
It is to avoid the handful of mistakes that can prevent you from staying in the game long enough for compounding to do its work.
