It really depends on what you're holding.  Many of the most successful investors have primarily got to where they are by investing in low-risk, low-reward investments and just holding them for many years (like Warren Buffet for example).

In Bitcoin's case, it's an even better choice to just hold if you're not much of a trader, because it's extremely difficult to predict the future prices when the primary basis for recent price has been speculation rather than usage.
You need to be questioning why you bought back in as much as why you sold.  Both were equally emotionally charged decisions.