If you're feeling sad, sit down and write. It could be a letter to someone or just a diary entry. Simple insult about person's fatness or disability may seem to have no effect at all, but often it does. Targeted peron doesn't want to seem weak and pretends it did no harm. The way to reverse it is to put some weight onto the opposite side of the plank - do a compliment opposite to initial isult or cancel the insult.
Insults are a complex issue, let's start from the basic purpose of insults.
The primitive, uncivilised way to increase your mood and self-oppinion is to decrease others'. By putting someone down primitives put themselves up, feel the power over somebody. The reason for calling them primitives is that good people don't feel good about putting others down because they experience another ways of interactions which put both sides up without putting anyone or anything down. This primal way includes such things as sarcastic remarks about someone, but their effect is usually minor and is usually retaliated back painlessly. Other reason for insult is not being able to express positive feeling towards a person, not being able to show affection in a right way.