I've seen a lot of writers say that sending their work out into the world is scary, and that rejections and criticisms are soul-crushing. I don't feel that way. I'd call it having a thick skin, but I don't think that's really it.
I have lived with depression for years, and anxiety and lack of confidence for my entire life (a doctor doing some depression questionnaire once asked me if I ever had days where I felt less than confident in myself, or some similar phrasing, and I literally had to ask her what confidence felt like because I had never felt it before). It was not a happy life by any means, and I genuinely despised myself as a person for longer than I want to admit. But it's made me a little bit fearless.
What's the worst someone could say about my writing? That it's awful? That I have no business mutilating the English language like that? That I stole all my ideas from movies and video games and mashed-together clichés? That if I'm really so stupid to think I have any talent, I don't deserve to live?
Realistically, no agent or publisher or beta reader would ever say anything like that. Even my worst enemies (and I do have a few of those) wouldn't say it. But if they did? So what? Nothing I haven't said to myself.
There is nothing bad anyone can ever say to me that is worse than the things I've said to myself, that I've truly believed with all of my sad little heart.
That powerful realization has given me, if not confidence, something at least resembling that elusive emotion. I'm still insecure, with my writing and in real life. I still worry that I won't be good enough, that people will think I'm mean when I'm trying to be funny, that my hair is too messy... And when people do say not so nice things, it does still hurt. A lot.
But there's something to be said for the ability to go out into the world and say, "Do your worst; there's no room for any more scars."