there is really nothing to regret, we learn through mistakes and we are told experience is the best teacher, the beans is spilled and there's nothing you can do. what you can do however use to use the other remaining half to get what you lost and more
yes, we have this lesson so we don't have to do the same mistakes. I learn many things from my loss and right now, I try to sell some coins that increase although I know that the increase of the price is not too high but at least, I can take a profit which I can use for buying other coins that might be profitable in the short-term.