We can only regret what we've done in the past but don't forget that we still have a future that will be better than the past and present if we keep trying in earnest...
Even now, when we sell or buy a coin, after a relatively short period of time, we clearly see our mistakes and lost profits. All these mistakes should help us to avoid them in the future and we do not need to dwell on it, otherwise we will not be able to move forward.