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
This has been discussed at length many times, if you are planning to become a trader then as long as you have a solid money management strategy then you can invest in a great deal of coins and see if your strategy is profitable when trading them, however if your intent is to become an investor and hold your coins for the long term then there is only one coin in which you can invest and that is bitcoin, even ethereum which is a good coin does not deserve to be in the same level as bitcoin as ethereum could at some point be replaced by a better coin, while the chances this happens to bitcoin are incredibly low.