Bitcoin is more of an investment instrument, a "digital gold". The price of gold also fluctuates, on a lesser scale but it is expected considering the fact that gold is known for many centuries, but bitcoin is still in its early stage. Exchange rates of different currencies also fluctuate.
The fluctuations in Bitcoin market is useful as well as not useful for some kind of people who have emergencies and can not wait for their profits to sell out the coins a get the profit to meet their sudden needs, this is because they took the wrong decision to invest all of their wealth here.
We know that it is market and anything can happen here. The price decrease gives us another opportunity to invest at low market as we know that the price is achievable at low price and in future the profit is ours because the market will surely go high again.