Some exchanges support the "trailing stop" function. It can be used as a stop-loss feature. You set a bid order for selling your coins. Also you define the sell value which should be below the market price by several percent. The trailing stop follows the market price if it grows. When this price is reduced to the value you defined, this order is completed. Thus the exchange can automatically sell your crypto-currency and you do not need to watch the coin price and be aware of the current positive movement trend.