If you are feeling depressed and negative, it is crucial for you to keep active. The less you feel like being active, and the more you just want to wallow in self-pity, the more important it is that you get out, interact with positive people, begin projects, and keep active. Until you begin to feel a desire to be active, just fake it -- go through the motions of keeping active until you can generate the positive attitude to drive your activity.
Positivity is contagious - so is negativity. Choose to spend more time with people who think positively, speak positively, and support your vision, your life purpose, and your projects. Spend less time with people who talk about how hard and unfair life is. Spend less time with people who tell you that your goals are unrealistic and that you are certain to fail.