Why I Stopped Catching Falling Knives: The Dangerous Trap of “Keep Buying the Dip”

Painless AI Lab – A Hong Kong Practitioner’s Real-World AI Journey (Part 11)

In my last post, we got into the weeds of “Market Signals” and risk management. If you missed it, the short version is pretty simple: my absolute core belief when it comes to investing is that if you can just avoid making the fatal, stupid mistakes, your chances of long-term success skyrocket.

Living in a hyper-dense, fast-paced global financial hub like Hong Kong, the financial pressure is incredibly real. Energy prices are up, rent is wild, eating out adds up fast, and honestly, the margin for error with our hard-earned savings is razor-thin. We simply cannot afford to let our capital disappear into a black hole.

That brings me to a massive mistake I see almost every retail investor make. It’s a psychological trap that feels entirely logical on paper, but can completely wreck your portfolio in reality.

Let’s talk about what you do when you actually find a winner—a valuable company with massive cash cow potential, a strong position in a hot sector, and high entry barriers.

What is my ultimate strategy? Keep buying.

But how you keep buying makes all the difference? 

Catching a Falling Knife

Most people are wired to buy more shares when the price drops. You’ve probably heard it a thousand times on financial forums: “Buy the dip! It’s on sale!”

The logic goes like this: you buy a US stock at $100. It drops to $80. Your brain tells you, “Hey, if I buy more now, my average cost drops to $90, and I’ll break even much faster when it bounces back.” Economists call this “averaging down.”

I call it a trap.

When you add shares to a dropping stock, you are fighting the market. You are assuming you are smarter than the collective wisdom of thousands of other traders. If that stock keeps falling, your losses don’t just grow – they multiply. Suddenly, you’re stuck in a zombie position, your capital is frozen, and you are paralyzed by hope.

If you do this with a stable, mature value stock, your main loss is opportunity cost –your money sits there rotting instead of working for you elsewhere. But if you do this with a volatile, high-beta stock? It’s an absolute disaster.

I’ll be completely honest with you: I learned this the hard way during my early days of trading US tech stocks. I found a company I thought was indestructible. When it dropped  5%, I bought more. When it dropped another 10%, I doubled down, desperate to lower my average price. By the time I finally swallowed my pride and cut my losses, a massive chunk of my trading capital was gone. It hurt, and it was a brutal wake-up call.

Flipping the Script: Buying on the Way Up

These days, I do the exact opposite. I prefer to add to my positions only when the price goes up.

Yes, this means my moving average price increases. It feels entirely counterintuitive at first because we’re conditioned to look for discounts. But let’s look at what is actually happening when you buy into strength:

• Market Validation: A rising stock price is proof that your thesis is working. The market is actively agreeing with you.
• Risk Minimization: You are scaling into a winning position, not trying to rescue a sinking ship.
• Psychological Peace: Your overall account balance stays green, which keeps your emotions calm and prevents panic selling.

Think of it this way: if you’re running a business here in HK, and one of your products starts selling like crazy while another one completely flops, where are you going to invest your marketing budget? You pour it into the winner. You don’t throw money at the flop, hoping people will suddenly change their minds. 

How My System Handles This? 

When I filter companies through the stock analysis system I’ve been building, I look for those rock-solid fundamentals. Once I find a target, I start with a small, baseline position.

If the price goes sideways or dips? I sit on my hands. I do nothing. The market hasn’t proven me right yet, so I don’t give it any more of my cash.

But if the stock breaks out and starts climbing, that is my green light. I keep buying. Even though my average cost is rising, I am compounding my wins and riding a wave of real momentum. It transforms investing from a stressful game of catching falling knives into a structured, peaceful process. 

What’s Your Strategy?

It takes a lot of mental rewiring to feel comfortable buying a stock that is more expensive today than it was last week. It goes against our basic human instinct to hunt for a bargain.

Have you ever fallen into the trap of averaging down, only to watch the stock sink even further?

Or do you prefer the peace of mind that comes with buying into a rising trend?

Let me know in the comments below—I’d love to hear how you manage this mental hurdle.