I'll be completely honest. When I first started setting up my SIPs, I thought the hardest part of personal finance was over. I spent days reading up on large caps, mid caps, and flexi caps, finally picked a few funds, automated the monthly debit, and went on with my life. "Set it and forget it" is the golden rule of passive investing, right? I felt like a financial genius because 50% of my income was automatically going into wealth creation every single month while I focused on my corporate job.
Then, a massive market run happened, and I opened my investment app. My small cap and mid cap funds were absolutely soaring. On paper, my net worth looked incredible. But when I actually sat down with a calculator and looked at the percentages, I realized something terrifying. The portfolio I had carefully designed to fit my exact risk appetite didn't exist anymore.
I'm no financial guru, and I'm still figuring this out alongside you. I genuinely used to think that if a mutual fund grows fast, there is absolutely zero issue. Why would anyone complain about making too much money? But here is what I learned the hard way: when one segment of the market goes on a wild, roaring run, it quietly warps your entire portfolio. It turns what was supposed to be a stable, balanced plan into a high-risk gamble without you ever clicking "buy."
The hidden trap of portfolio drift
When you first design your investment plan, you split your money based on how much risk you can handle. But different types of mutual funds grow at completely different speeds. Over a year or two, those different speeds completely distort your original balance. In the investing world, this distortion is called portfolio drift.
Let's look at a hypothetical example using a ₹15,000 monthly SIP allocation to see how this plays out in the real world.
Imagine you start with a logical, three-way split based on a standard growth strategy:
- Large Cap / Index Funds: 50% (₹7,500) - your stable foundation
- Mid Cap Funds: 30% (₹4,500) - your growth engine
- Small Cap Funds: 20% (₹3,000) - your aggressive spurt
Now, let's say India experiences a massive small cap and mid cap rally over the next two years. Your small caps grow at an insane 25% return, your mid caps do great at 18%, but your stable large caps grow at a modest 10%.
Because you set up automated SIPs, you haven't changed a thing. You are still putting the exact same rupee amounts into the app every month. But because the small and mid cap funds grew so much faster, the total value of your accumulated wealth has completely shifted shape.
Without you realizing it, your actual portfolio balance now looks like this:
- Large Cap: 35%
- Mid Cap: 35%
- Small Cap: 30%
You still think you are playing it safe with a 50% large cap safety net. In reality, 65% of your hard-earned money is now sitting in highly volatile, aggressive segments. When the market inevitably gets tired and corrects, your portfolio will bleed much faster and deeper than you ever planned for.
That is the issue with a fund growing too fast. It forces you to take on massive amounts of risk that you never actually agreed to.
The psychology of selling your winners
Fixing this drift is called rebalancing. It isn't about trying to time the market, predicting the next budget, or chasing hot new trends. It is simply the mechanical, unemotional process of bringing your portfolio back to your original target asset allocation.
But I'll be real with you - the psychology behind it is incredibly difficult to wrap your head around.
Rebalancing forces you to do the most counterintuitive thing in investing: sell your best performers and buy more of your underperformers. Every human instinct tells you to do the opposite. When you see a small cap fund delivering amazing returns, you want to feed it more money. When you see a large cap index fund moving slowly, you want to ignore it.
To rebalance, you have to look at the fund that has been making you look like a genius, consciously cut it back, and move that money into the boring fund that underperformed. It feels like benching your star cricket batsman to give more time to someone struggling for form. But in investing, this mechanical process is how you actually lock in your profits at the peak and force yourself to buy stable assets while they are relatively cheap.
Should you rebalance?
Rebalance if:
- Any single fund category has drifted more than 5-10% away from your original target allocation
- You haven't looked at your portfolio percentages in over a year
- A major market rally has made your small or mid cap holdings disproportionately large
- You're closer to a financial goal and need to de-risk
Hold off if:
- The drift is minor, say 2-3% off target - transaction costs and exit loads may not be worth it
- The drift only just started a few weeks ago - give it a quarter before acting
💡 Tip: Set a recurring calendar reminder every January to log into your investment app and check the actual percentage split - not just the returns. Ten minutes once a year is all it takes. Most apps like Groww and Zerodha Coin show the current allocation breakdown right on the portfolio screen.
Final word
Managing your money isn't a one-time event that you set up at 22 and never look at again. It is a dynamic system that needs an annual check, like a car service you keep pushing off until something actually breaks.
Your portfolio is a lot like a garden. Letting your automated SIPs run month after month is how you allow the plants to grow. But an annual rebalancing check is the essential pruning that keeps the aggressive weeds from completely taking over the space.
How long has it been since you checked the actual percentage split of your mutual funds? If your small caps have been running wild, it might be time to log into your app this weekend and look at the real numbers.
Drop a comment below and let me know if your portfolio has drifted out of bounds. Next week I'll walk you through the exact step-by-step math on how to fix this drift without getting hit by heavy Indian taxes and exit loads. Let's figure it out together.