It’s not impossible. Even broken bones eventually mend themselves, if the victim manages to live through the injury, isn’t prey to attacks, and can have some time to recuperate. The body ‘can’ heal many diseases and injuries on its own (even smallpox, as deadly as that often can be / has been) isn’t 100% lethal. But I wouldn’t counsel this as “the way to fix depression”, either. I’m glad you survived; please don’t recommend that others just “ignore it and it’ll go away”.