Bitcoin is dumping because whatever goes up must come down. You don't expect bitcoin to keep going in same upward direction without correction. What you need to do is either you are a short term holder, then study your chart and know when to sell and rebuy. If that would be so difficult for you, simply become a long term holder and forget about the changing prices and be assured of your results on the long run. Bitcoin is cyclical and there's nothing we can do to change its nature.
Bitcoin price fluctuations are forever unavoidable making it possible for traders to gain and lose in the short and long term.
Avoiding short-term fluctuations may be better by holding bitcoin longer, but still many traders will consider short-term trading because they are able to master a good trading strategy. As long as they can afford it, they can trade for the time frame as they want.