No one knows the future and I am sure a lot of us based our decisions totally on that which is human unless you are extremely principled which everyone should anyway. Nevertheless, sometimes, we do always wish we can change back the hands of time, but since we cannot, we just have to move forward and re-fix the future to our best.
For an average bitcoiner, it's really normal if we see lots of them do sells because of various reasons, like you said based on our decision. There are times that people needs money, needs profit, scared of price decrease that's why they are ignoring the principle of long term holding. It's not wrong after all because that is their coins after all and only they are the one who can do whatever they want to their precious coins.
I sometimes dump too but not that much since I have a spare. Selling is part of the cycle so just enjoy the game as long as everyone knows what they do.