It really depends if you are an investor or a trader. Investor mainly hold Bitcoin as long as they can, or at least if they reach their target price. They usually hold it for years and let it appreciate overtime. They tend to be calm even it dips or the market corrects. They see this as an opportunity to add more to their holdings. On the other hand, traders have different approach to this. Some are day trading which usually hold within a day and sell it for a profit. This is commonly called as scalping. Others are for short or mid term. Usually they hold it for days to weeks or even months. They have a setup for this kind of trading and let the market do the work. As you can see there are many reasons for people to sell their Bitcoins. As they always says, "Plan your trade, trade your plan"