Just match the investment plan before you buy bitcoin, if you plan to sell it when you get profit then the best thing is you have to sell it. Then how about the price of bitcoin in 2019?
Before answering, this lets us learn first
Look at predicting prices I think all of that is just a technique that has not reached 100% accurate, even not up to 50%, so in my opinion there is no certainty whether bitcoin will rise in 2019
Be patience, Pray and sure this is one of the easy ways to invest even those who use this method do not care even though the price falls, and on average they get very large profits, but the time needed reaches 1-5 years (like the name of investment sure that need a long time to get bigger profit.
If you have the characteristics that I mentioned above, yes you will get a very high profit