Well, what else can we do? If we saw our coin plunge we should take the opportunity to accumulate and then just HODL it, if it surges then sell. No one will set at a low price though so what's our choice?
The coins I think better on these buy and HODL strategies are the less volatile one like Bitcoin and Ethereum but if it is an altcoin mostly, you won't be needing to HODL I guess, the fact that most of the altcoins are highly volatile.