So I'm working through my daily anxieties in therapy and the thought occurred to me - how am I supposed to trust myself while questioning the accuracy of all this?

I don't know when it happened but I've gradually become painfully insecure and I struggle a lot with feeling/seeming to appear stupid and incompetent. Even a typo makes me cringe as I imagine how I must be judged and mocked. When people laugh in public I immediately suspect they're laughing about me. I dislike even being around others at this point because being perceived at all is exhausting. And I understand these things can ironically sound selfish or inflated, which further complicates my feelings.

Anyway thoughts, feelings stemming from fear ... I want to let them pass naturally, not attach to them so much, not accept them as true. But my world starts unraveling when I examine them because I can no longer tell what's true and what isn't (I know, I know - black and white thinking). And I couldn't trust myself in the first place, or even identify which parts were me (though to be fair that's less anxiety and more a matter of existentialism), so how can I protect myself at a time when I especially need confidence but am supposed to be self-critical?

Are there specific things y'all tell yourselves when engaging in this work? "My anxiety is not me", "it's okay to let even parts of my actual self go", "I can create new beliefs", or just "I trust myself"? How do you reconcile yourself to accept those statements? Are there exercises that strengthen your self-trust and help you separate your self from your anxiety?