lets see if i can help you:

knowledge is a justified, true belief. if you disbelieve something you can’t “know it”. similarly, if your justification is insufficient, you can’t know it. finally, if it actually isn’t true (which would be a good reason it lacks justification), you also can’t know it.

i can’t help with the depression but i might be able to help alleviate the guilt. is there some particular fact that you think is the crux of it all, which, if you didn’t believe it, or found your justification was insufficient, or just that it’s not true, you would be happier? i’m pretty good at evaluating positive claims and determining whether they are rational.