I know bitcoin when it's around $500, if I am not wrong, and I have bought and held it for a certain period of time. But I had to sell it before the bull in 2017 happened which gave me regret. So, not everyone who knows bitcoin earlier will get the maximum benefit from the last bull run.
No need to regret too much mate, I believe you are not the only one who did not manage to sell what you hold for some period of time at the ATH. I'm sure no one even predicted that it would reach that price at the end of 2017. As long as we are making some profit, then we should not regret it too much. The chance to make more money through bitcoin is still exist, hold for the next bull run although we do not know when the time will come.