If it is a future trading, I have lost more than 10x 
if it is a spot traidng, I will prefer to set cutloss if it is possible and also see the trend of the market itself.
But once forgeting to use a CL or SL< I will prefer to hold the coins untuk the price is gettng increased (FYI, this only =for top coins or potential coins for holding, if not, better to set SL)

About what amount to lose, I am sure that everybody has their own ways adn amount. But at elast, just loose what you can afford, never folow the hype and always do our own research including how much we are going to put into the coins.