I think even the one who have sold few % of their bitcoin have already bought back bitcoins at higher price because they don't want to miss the current bull run. I have done the same, I have sold at low price and bought back at high price. You can call me panic buyer/seller but my decision already turns out to be right one. 
You have done wrong that you have sold at low price you should need to trust bitcoin as according to rules because bitcoin is giving opportunity to people so how you can say that you have sold in low price you should need to wait for bitcoin that it will go and go again to high prices because bitcoin has never done something wrong like that so what do you think?Its always good to hold bitcoins for a long term and to be honest I really don't know which is the best price to sell bitcoins as if I see today then tomorrow I may see much higher price in compare of today so sell it only if you need money or if you are completely satisfied with the profits that you are making.
Only 2 reasons to sell btc - you need money for bills or you believe the price is going to come down and you can come ahead btc when it does by rebuying.
Otherwise, use it to make more of it by buying shitcoins like bch, omg, etc etc etc.
