Better to hold that coin if the value is very low. It's value takes time to increase and that is the time to sell it. But if your coin has high value now. Better to sell it than losing profit.
This is not the time to sell any cryptocurrency as it is very cheap now. wait at least for this winter. As for me, I am planning to hold my altcoins (NEO, Komodo, and Lisk) for at least 1 year more.
I suggest its better to know if your coin have potential because if it is then its better to hold it but if not then its better to sell it, if your coin have potential then hold it because surely gives you a lot of earning. While if your coin have no potential then its better to sell it and buy another that have potential like Ethereum or Bitcoin because surely give you more profit and also this two crypto are successful so there's nothing to worry if your goin to jold it or sell it.