Engage in charities: you will feel well and very satisfied when you contribute to a good and positive cause. This is also a great opportunity to meet people and make new friends.

Try and find a non-profit organization that helps a cause that you can identify yourself with. If you don't know, try Volunteer Match. If you do not live in the United States it could still be interesting to look into the site to see all the kinds of charities available and then find some in your country.