For me i will consider the price before selling.I will assure that i gained a small profit.Read news about the market movement and if see that i will gain a litle bit money thats the time i will decide to sell.
If you sell without any profits -> There are two chances -> You are a dumbass / you clearly forgot to put a stop loss.
Those are the only reasons, but i do not like to sell my cryptos, maybe that is the reason of why i have a lot of useless tokens on my MEW; it is like something usual for me.