When you lose a big win, it is always very painful and difficult to forget, it's not because of the money but the game since you have being working very hard to have that win and it is close to you but due to one mistake or the other, it was a narrow escape to lose, it is not always easy to come out of that shock.
When you considered losing a game a mistake from your end, you might have been blaming yourself for something you owe yourself no explanation for. I mean, in gambling, you have to try out your luck to see how you can be able to increase your chance of winning. If that skill and your luck did not allow you to win, that's not because of your mistake but because it's gambling, and you should accept it in good faith. It's painful to lose, but what's more painful is blaming yourself as being the cause of your failure. It's good to take responsibility for your actions, but not in this case.