I used to feel regret like you but after many times like that, I no longer react that way. Nowadays, I feel happy when I take profit and don't care, don't feel regret if price rises more. Profit means happiness. Profit is my aim for trading or investing.
I missed the entire DeX coins and i am not confident to enter at this valuation because if the market goes down the entire market will go down along with it. There is no point in regretting, in the past i used to hold the alts for the long term and i missed a lot of opportunities to sell at an high but now i have my target about the profit i want and there is no point in regretting in this market.