The 5 position-sizing mistakes beginners make most

When I went back over my losses from 2021 to 2022, I found one thing: the bulk of what I lost wasn't from misreading some coin, it was from failing, again and again, to manage my position. A mistake in picking a coin at most makes you earn less; a mistake in sizing can break bones. The five below are ones I stepped on myself and have watched newcomers repeat over and over.

Mistake 1: going all in from day one

This was the first I made, and the most expensive. In 2021, watching the market climb and terrified of missing out, I bought almost all of a big sum I'd saved in one go. It pulled back right after I bought — one foot planted squarely at the top.

The problem with going all in isn't just “you might buy the top,” it's that it uses up all your room to maneuver. The money is all in, and when it really falls you have neither bullets to add nor any nerve left — because what you've lost is the whole thing, not a part.

The fix: split this money up and get in over several buys. You can dollar-cost average monthly, or invest half now and split the rest. How exactly to split it I wrote in DCA or lump sum.

Mistake 2: topping up more and more, with no cap

Topping up isn't a bad thing. What's bad is topping up with no cap. Plenty of people (me back then included) think like this: it fell? Great, it's cheaper, add a bit and lower my cost. So you add more the further it falls, and topping up turns into pouring in money you never planned to invest, one batch at a time.

That's how “investing spare money” slides into “endlessly filling the pit with new money to rescue the earlier batch.” Once it keeps falling, you're not down one share — you're down a ball of losses that keeps rolling bigger. I've watched people top up with their emergency fund, even borrowed money, until it broke through and the loss was far beyond what they could bear.

The fix: set the rule in stone before you top up — what your total investment cap is, the maximum number of times you'll add, and the level at which you stop completely. Write it down, execute it as it falls, don't change it on the spot. Topping up is a planned action, not a reaction to being worked up.

Mistake 3: treating living costs as spare money

“It's all spare money I'm investing” — many say it lightly, but pick at it a little and the truth shows. The so-called “spare money” is often next quarter's rent, your kid's tuition, or the part that should be set aside for emergencies. It's spare now only because the time to use it hasn't come yet.

The biggest risk of investing this kind of money isn't the loss, it's that time will force you to sell at the worst possible level. Some day you urgently need cash, and it happens to coincide with the market at the bottom, so you have no choice but to sell at a loss. I wrote a separate piece on this — before you get in, set aside your emergency money.

The fix: before you invest, ask one question — if this money stayed locked away for three years, would my life be affected? If yes, it's not spare money. Set aside 3 to 6 months of living costs as an emergency fund first; only what's left enters the “investable” pool.

Mistake 4: adding because others are heavy

In group chats, comment sections, and short videos, there's always someone flaunting a heavy position and a profit, and it looks awfully tempting. You start muttering to yourself: they invested that much and made money, am I being too timid with my little bit? So you quietly bump up your position.

There are two things here you can't see. First, you can't see their full picture — how deep their net worth is, how strong their tolerance, what share this is of their total assets, you have no idea; that number might be a drop in the bucket for them. Second, you don't see them when they're down. People flaunting profits far outnumber those flaunting losses. You think you're seeing the norm; you're really seeing the survivors.

The fix: take other people's positions out of your decision entirely. Your cap depends only on your own income and net worth. How much anyone else invested has not a cent to do with you.

Mistake 5: scaling up after a gain

This mistake is the most hidden, because it happens when you're riding a tailwind. The account is up a stretch, the paper gains make you feel you've “got it figured out” and “have a feel for it,” and bit by bit you scale your position larger and larger, even past the cap you originally set.

The problem is that paper gains systematically make you overestimate yourself. You mistake luck for skill. When the market pulls back, you bear the fall on a higher position, and you may well give back both principal and profit, even end up net down. That was me in 2021 — I added aggressively in the bull, felt great about myself, and when it fell those additions became the deep wounds.

The fix: tell two things apart — “scaling up with money already earned, in step with the trend” is a choice within the rules, but “breaking through your set cap because you're worked up” is dangerous. The moment you're making money is exactly the moment to glance back and check whether that cap of yours still stands.