It sounds simple, but it is difficult to perform. The volatility is really unusual.
But the history of bitcoin has shown that, in general, if you hold you win.

Well that sums up all things pretty well, since the history of bitcoin told us that wether there's a big dump on a coin it will still recover and make a new-step on it's way. So whatever the price will be wether down by 10% of it's current price, it will still increase as time goes by.
But we must not always depend on history as a gauge on how things are going to be in the future. There are other things that come into play whenever the price behaves rather wildly. For what it's worth, I am only investing what I am willing to lose.