I would strongly disagree. Selling your Bitcoin in a strong downtrend is the SMARTEST decision you can make. There is something called stop loss - use it or lose it!!
Buy back below 10K
What if bitcoin never got to the 10k and just suddenly pumped back up in prices? Would it still be good? I agree it is a smart decision but for those with a really short-term goal only, if you are a long-term one though, you can hodl and buy more when the prices really did went that way.