It looks like selling your crypto for money when they are profitable is more safer than holding them for long, my point is only very few coins are worth holding for many years, if you still doubt about this go on coinmarketcap and look at most coins that came into this world in 2018 many of them have no volume again, the shocking one to me is gowithmi, a project that my elder brother praised so much at the time but today it's volume is not up to 50k, many projects will face same fate, be smart
It's going to repeat from time to time.
And one day soon there will be fewer cryptocurrencies in the market and the majority that stands long together with bitcoin might have not been seen yet and the rest of the top are likely to stay.
It's both safe, to sell at profit and to hold if you want to.
I'm doing both, selling when I'm in profit but I'm also holding as you've said, the biggest part of portfolio because I know that it's the best to hold on the market.