a long time ago i learn a valuable lesson and i will be using it as my main goal. let me share it with you.
it is important to sell when you are in profit. in altcoins it becomes a lot more important because they are not stable investments and they have the high chance of getting dumped. and they do get dumped a lot after each pump.
but we can never predict anything in a manipulated market of altcoins with lots of pumping groups all around it. what that means is that sometimes you sell too soon or sometimes you sell and price goes up afterwards. there is no reason to worry about it, you can still buy back! nobody is preventing you to buy back saying you sold so you can't now

so what i do is that i simply buy back when i see such a pump is going on and enjoy the additional profit that i am gaining. but that still doesn't mean i won't sell when price is at the bottom and not moving at all just because i hope it can go up!