Yeah, profit earning from bitcoin depends on the time of selling and time of buying so we should remain careful before buying or selling our coins. When the market is dump we simply should buy and if the market is green we can sell. So good time will come very soon its just a temporary fall of the price that will not take much time to recover again so keep holding.
It is not always the case to buy and sell ahead with the indication of green and red market. Most of the time, real profits can be get from thinking and waiting for a long time, and to research about the ATH and ATL, if we are always buying and selling we cannot maximize our investment but if we are buying and selling with the ATH and ATL, that's the time that we really earn huge profits. But I can assure you it is very hard and require huge knowledge about combined trading from the concepts of stocks and cryptocurrency.