First of all, you have to decide what to do, when you buy and quit. Never and never invest all your investment in a single coin. Choose at least 5 coins and divide your investment into 5 coins. So you can reduce the risk of losing.
The only way to manage the risk in investing in cryptpcurrency is oonly invest on crypto that have a great chance to rise in the future just like investing in bitcoin and off course to manage the risk you should only invest when you feel that the market will start to rise again.