I agree with what others have said. If you really think bitcoin is going to tank to 50$ then yes you should obviously sell before you take more loses. When the downtrend started I sold my 10 coins at 551$ with an average buy price of 530. I looked at it that I was protecting my 5k+ investment and planned on buying later at a lower price. I too have been disappointed with what has been happening, I had an average buy of 450 but then I bought some more in the 500s and 2 in the low 600s which took my average buy price out of the 400s.

So I'm hoping to buy lower, but I speculate that bitcoin will go back up. (I'm actually thinking of buying at 520$ it is at right now at the time of this post but I think it will go down a little further)