I have learnt my lesson from 2018. Had just got in to Crypto and HODL'd all the way thinking it would keep going up. It didn't. So now I always take profits. everytime BTC has hit an ATH I've been taking profits and now have a healthy amount with a good amount of BTC still left over. My advice would be to always take profits when you can.
Well, all I can say to that is that I took profits in 2014. And regretted it for a long time.
The thing to do, in my opinion, is learn about Bitcoin. There are tons of resources out there from books, articles, videos, podcasts, etc. Once you get proper perspective, the smart move is Hold On for Dear Life. Maybe sell a little bit as it goes up if you want, but always have a core position. Same thing as the people who held onto their Apple, Google, Amazon shares etc... The ones who took profits early are the ones who are crying now.