Like LynnP says...rigorous physical exerise.
I'm a bit of a couch potato, so I'm not here to advocate it personally, but I HAVE noticed, among the people I know, that those who are into regular physical fitness, besides looking great!, have few emotional problems. They exude confidence, don't seem insecure, and interaction with them is always positive. I may try to develop a healthy exercise routine to see if it works...May...hmmm...