Yeah that is the thing with selling bitcoins - you have no regrets for like a whole week, then maybe a month of being happy that you got out on "top", and then you regret it for the rest of your life
I have regrets almost every time cause I'm cautious (or scared) and usually sell long before the top. IMO he did good - left himself 20% and sold the rest so he can still profit. His 20% can still be more than most of us hold. If you hold big it's perfectly normal to be scared when it goes up like it did last week.