You can't hold Bitcoin forever, atleast for my understanding because you can't be holding something in secrete that you don't want anybody to know because of privacy reasons. God forbid, what happen when you keep holding forever and then one day you died and nobody know you own Bitcoin and even they do, not like you wrote a will somewhere that you want it to be access and I doubt if it's even sate to write a will about holding a bitcoin in the first place.

Sell if when you have had enough profits but don't sell everything, sell when you know you have achieved the goal of holding like for instance, we have people that are holding Bitcoin from 2009, their goal could be because they want to hold it till Bitcoin cross over $100k be for they sell and it cool but sell when you think it's right, no point in holding forever except there is a way which your keys can be access when you don't breathe air again.