To defeat the unhealthy emotion, what you need is a heavy dose of positivity and the drive to move out of its spell.  You can get help from a psychiatrist, since shrinks are trained to deal with all types of problems.  Your closest friends will also come in the picture, as they offer you support and some inspiring words.  If you use all of your resources, you’ll eventually break away from depression.  Perpetual happiness is the reward for your efforts.