Always have an exit strategy. Maybe you can stand to lose 20% before you sell and try to reevaluate where the market is heading. And vice versa if you can feel good about selling a coin that has gone up 3x, maybe leave some coins to see if it rises further, but being ok if you sold at 3x an then later it goes to 10x. There's no need to be so zealous about coin investment. Just know where you're comfortable getting out on both sides.
If you have a chance to take profit a cryptocurrency at 3x value, and as you said, you still feel that coin can increase in the value, you can make a profit 50% that amount or enough the amount you invested. That's my strategy to deal with this case because sometimes, some altcoins won't stop the bullish trend early as you predict. This strategy helps you can evade the situation you miss the chance to sell at high price.