People tend to have a stronger opinion of themselves than anyone else has of them. For as selfish as this may seem, it's healthy. However, it's not healthy for that opinion to be exclusively negative. You are either your own most vocal supporter or your own most vocal critic, or both. But if you're solely your own most vocal critic, there's something wrong. amirite?
The world around us treats this sort of mental condition as a joke, especially when it afflicts unattractive or unkind people, but in truth, it can ruin your life no matter who you are. It has nothing to do with being weak. In fact, it will hurt you all the more if you're strong enough to endure it, because then you won't run away into suicide.