"Don't sweat it" is the most important thing, I've found, especially with tinnitus.

As with a number of things, I've found I can actually move the needle when I give myself grace to fail, as long as I can genuinely try again and resolve to do better. A recent example being stopping telling myself I'm tired in the morning. Such a bad habit that self perpetuated. I was always feeling tired, in part, because I was telling myself I was tired.

Chewing fingernails on the other hand, damn... that hasn't worked so far because I give myself grace, but never really resolve to do better. Someday I'll figure that out.