That's some of the rare philosophical aspect of finance/trading. Every body has sold assets that ended up exploding (Tesla or else, and bitcoin amplified this, many people had millions in their hand virtually but gave it up for a pizza).

It teaches you not to focus on regret and only care about risk/satisfaction ratio, and to keep moving.

This topic also tailor your sense of self too. When you made a few too many bad choices (job, relationship, location) you get a finer sense of what you want.