I regret not selling my coins in January 2018. I keep them today. I was led to a long-term coin-holding of randomness. He did not sell the coins and became no longer a long-term investor. Now it makes no sense to sell, I will keep on my coins - it turns out for a long time.
it make sense to sell if you think that the price for bitcoin will drop even lower. You can sell now at 4200 so then you can buy for $ 1,000 again, for example. I'm not saying that this will happen, but it is possible. then you will have more bitcoin than now