For me too much deep introspection does lead to depression. I am fully capable of diving into my navel, and it turns out to be a deep dark pit. Doing anything productive, or even just fun, is a cure for me. I often read the news, feel miserable about the state of the world, and then go outside and do yardwork, get my body in motion, and very soon feel much better about the world and my place in it. For me introspection isn't bad in itself, but binging on it is, as with food.