I have this and I must say the important thing is to stay off any kinds of medication, which seem to work at first but then side effects like obesity and antisocial behavior lead to low self esteem making it worse.
Your hormones or diet might be out of balance - some foods can cause lethargy or depression, while others can do the opposite. My advice from personal experience is
1. build a very strong social network and hang out with lots of different people you enjoy spending time with
2. participate in social activities like sports, group movies, or games
3. yoga or martial arts to help develop confidence and energy
4. distracting projects, like building a bird feeder, scrap booking, sewing, or remodeling
5. school or if you have a job, take some of those 0 credit courses or part time enrollment
6. go out with friends for lunch or dessert