This is indeed a tough one. It’s hard to sell when things are pumping and you don’t want to miss the top. But then you don’t want to miss the top and end up losing 90% value like that happened to most alts in 2019 after the pump. Controlling greed is key.
People should start to use their sense to determine which is the best time to sell our coins. I have seen that so many times people have not sold their coins when the bullish happened and they have ended in a big lose cuased by they can't take the opportunity and they keep hold their money in their wallet. That's something that must not be done by anyone.
People should sell at least some of their portfolios.
It is better to take some profits to prevent regrets just as the OP emphasized, with some little research a hodler should use indicators that can indicate overbought zone of the price RSI indicator is very helpful in that regard however when the price reached overbought zone it either price dump completely or pullback a bit before continuation of the bullish run however to be on a safer side it better to partially take some profits to avoid touching stories cryptos are highly volatile in nature.