Believe me, the regret when you see the price going up very high after you have sold early is more painful and makes you more restless than seeing the value of your assets or portfolio fluctuate, and I say that with experience and that's why I always recommend people to not panic after seeing short-term downfalls of Bitcoin or the market because once it goes up, you will have your wounds healed up pretty quick and the pleasure when you see your portfolio gaining value is extremely sweet.
Those who sell early, even if they have got a lot of profit based on when they made their purchases, will still regret their decisions when they see the highest prices of the cryptocurrencies they once had but sold them. If you have bought Bitcoin at $20k and then sold it at $40k but then you see Bitcoin hitting $100k during the bull run, how would you feel?
One who sold their asset earlier because of the thoughts that they will loss money if market goes down so when he see that market is going to increase day by day then this type of emotions are really sad for him. As we have seen bitcoin history so we should not rushes towards profit because the more you wait the more you will be profitable.
If someone get profit and sell their assets with profit then there is no need of regression but still human desires are incomplete always so they wishes that if they had huge profit than this then it will be better but a man always find an amount which is in his fate. If someone feel to regret for selling of bitcoin in past then he should remember that if he obtained benefit then don't be sad for it and try to be more profitable in future by buying more now.