You said sell now or you WILL regret it? Then it could also be Sell now and you will regret it.
I'm not saying that bitcoin will achieved a new ATH this time, but I do think that it can, or maybe it can reach 12k again, Last time, it sits a lot of weeks in 10-11k and went up later on. I might use that as another hope for holding some of it.

I'm not holding it for a long time though, if some signs says that it might fall later on, then I'll be considering selling it before that happens.