i dont sell. i will wait for 1000% or more.
because of this greed i lost half million dollar in 2018 january.
wow, lost a half million dollar is a huge money my friend
so, you should learn from your personal experience, don't be greedy, always set a realistic target price in your investments
for me 40 % - 100% profit is more than enough

It works both ways. Sell too early and you can lose half a million in potential profits.
But I do agree, typically choose a profit level and just go with it ... and maybe hold onto a portion of coins just in case prices do rise even more. You won't end up with the best price that way, but you also won't lose out much either.