Price of bitcoin increased because in 2017 many people get involved with it.
And old bitcoin users make HUGE profit, and new users Get scared.
What we need now, People need little study about what they wants to do.
If you guys invest at the middle stage price of bitcoin, all you need to do is to hodl and hodl, just dont panic, dont sell your coins on rush, just keep holding on until it will rise again. If it rise then thats the time to earn profit. Jus hodl it, if the price rise and reach to your expectation dont hesitate to sell it.