Yeah, none of this is bad advice at all.

In my normal personal life I tend to be pretty sarcastic and self-deprecating. My therapist says it might be a defense mechanism to avoid actually confronting problems; if you make a person you're talking to laugh then they usually think everything is fine and stop worrying about you.

I try not to do that during interviews. I don't think I'm coming off like I'm trying hard to be smart or brag, but it's very possible and likely that some level of my normal insecurities are bleeding through, and that happening even subtly might be enough to poison it for me.