You can't judge the quality of decisions you made in the past based on what you know now. Imagine going to a casino, putting $100 on red in the roulette wheel, black coming up and then thinking, "Man, I really regret putting it on red, I should have put it on black".

How is that in any way useful or going to improve future decisions? Bet on black, because you know, that's where the trend line is going?

Case in point: Do you short Bitcoin now or not? Who freaking knows...

Its still the right attitude to have or else every hindsight choice is going to be regret, and we'll be talking trillionaires. No one can predict the future. It could have gone down to 0.10 instead of up to 1000. Should everyone buy in now and expect the value to go up to 20k?

Do you regret not buying every penny stock that went up in value, every roulette ball that landed on red you didn't bet on? From a get rich quick standpoint there is no difference.