To answer the original question: selling now, when it is nearly 75% down, could be when most of the correction has already taken place. Maybe it will drop further, to $4k (80% correction), or even 90% @ 2k... IvanOnTech recently said this wasn't out the question, same as what Tone Vays thinks.
The question is: can you live with your long-term investment going down further, in the belief that it will still be worth much more in the future and even near-term (like in a few years even) or whether you can live with selling at a loss and in the future seeing that you could have crypto worth a lot more.
The choice is always yours, and what you are willing to live with.