The key component of depression that makes it so difficult to get out of depression is the belief that nothing you do will make any difference – so why even bother trying.  Fighting depression really means doing SOMETHING, anything, even though you “know” it won’t help, like there are two of you at the bottom of a well, neither of whom believes anything will change, but one of whom keeps throwing a grappling hook to the top anyway.  The act of throwing that grappling hook, even if it catches on nothing and keeps sliding back down to the bottom, is the act of believing in yourself – and that is what ultimately pulls you out.