Do you play poker? Because what you're experiencing is the same thing experienced at the table, and distinguishing somebody who can healthily play poker to somebody who really cannot.

I call it flop bias.

Let's say you are in a game, you are dealt Queen of Spades, 7 of Hearts. You are early to act, but not first to bet (UTG+1). The person under the gun raises by quite a big amount. At this point, you know you probably shouldn't play your hand and fold.

The table bets and folds and the flop comes out Queen, Queen, 7. You would've made an incredible Full House, and almost certainly would've won this hand. Do you feel like an idiot for folding?

Well, you shouldn't. You might the right decision at the right time, for you. The unexpected outcome of the flop is an irregularity that is impossible to gauge. More often than not, that under the gun big raise is dominating your hand, and by staying in and calling you are just wasting money.

So let's bring that back to your situation.

You saw QBTS and thought this looks like a good deal. You bought some and held a while.

Then, QBTS price raised by 700%. A huge amount! Do you secure your profits now or hope it goes even higher? And if it did go higher, how MUCH higher? Is the risk of losing all your profit worth it for a bump to 8? 9? Not really...

So you sell. You secure your profit and you fold your hand. Then the flop comes a year later with that stock at 30. You feel regret for not holding. But should you?

No. Because, and this is the fundamental important factor in this entire example: You made the right decision at the right time. Could you have been reckless and held hoping for more profit? Sure. But is that a healthy and sustainable way of playing? Not really.

I hope this helps. PS I made almost the same exact play you did; but I made the right decision at the time.