Fear is only of the possibilities you have already seen. Fear is only of the known. It is for a repeating of a possibility in your memory and proportional to how long it lasts. Fear arises when the input interpretation predicts/expects an unpleasant possibility.
When all that the input interpretation engine comes up with is outputting unpleasant, scary, horrible possibilities - that leads straight to depression.
But if nature is infinity possibility, there must be a way to move out of the hell realms into one of the earth or heaven realms. My fear is mainly getting stuck in some possibility. Now why do I get stuck? Because the possibility manifests with no energy/will/freedom to get out of it. Its like putting a dog in a cage, it cannot free itself by itself.