The best way to minimize future regret when you have big gains or losses is to sell some. There's no right amount, but for example, if you sell 20% and the stock doubles, hey, at least you still have 80% of it. On the other hand, if the stock gets cut in half, hey, at least you sold some of it. People tend to think in all or nothing terms, but it doesn't have to be that way. Thinking in absolutes is almost guaranteed to end with regret. Minimize regret and you'll maximize the chances of you being a successful investor over the long term.
