Agree! There are times that you need to sell your coin for you to earn profit. There are coins that are not for long term investment. If you keep on holding all your coins, thinking that it will increase in the long run, then you'll probably end up losing your money.
of course some altcoin also have a character of their own. take a look at dogecoin, they are suitable for the transfer of the assets of crypto as it is to the transaction fee of dogecoin is also very cheap. for some assets also has a very quick price change, I think such assets suitable for trade.