Hold only good coins, don't hold shitcoins. If you don't sure that coin will go to the moon, don't hold it, sell it if price falling.
In january I bought 1ST for 1$ and sell it in february for 0.7$, now price is 0.38$. I loss money, but only 30%, not 60%.
I agree with your opinion, indeed before holding a coin must note that the coins are good or not to hold in the long run or short. if you do not know clearly about the information about the coin then the result will be a loss