The human brain is a strange thing, you have to get 8 good things in your life to forget 1 bad thing.
It is made to focus on bad things first.

For exemple you can have a wonderful day, a good breakfast with someone you love, after you go to the cinema or the beach, have good news from your family...in the middle of all that, if someone tells you that you have a ugly face for no reason, this is the most powerful information which will be remembered by your brain.

And this little bad thing will make vanish all the good things....sorry about my english bro