Bitcoin price trends is upward. It is consistently rising, 2017 is the year for multiple all time high BTC prices and I know it will continue next year.
You can still buy BTC when it fells down a little bit because I don't want to think that it will hit a hard drop. Just feel the market and keep monitoring...
My biggest mistake is to invest in BTC. I bought a BTC at 15K and now the price of n is 11K. I lost a lot of money
That is the reason why there is always a right time to invest because not every season in the market is pumping and as of now if you are losing a huge amount profit then you should just hold your coins and do not sell them in the lowest price in order to reduce the probability of losing even more of your investment.