It always goes down and up, just because it goes down a bit there is no point on getting excited or scared. You can be rest assured that bitcoin will go both directions all the time. It will never be sort of coin that will either stay the same or at least move one direction, it will definetly move to all directions possible.

It goes up (like we saw last year when it hit 20 thousand dollars) it goes down (like we saw going down to 6 thousand dollars) and it goes sideways (like it has been for the past 5 months). Bitcoin usually goes down when there is someone that sells a lot of bitcoin at once or at least there is a market scare about something and people sell to get out, thats the only reason, more bitcoins sold than bought which causes the market to drop to cover the difference.