I've been day gaming regularly for 5 months, and everything has been up and down — sometimes rejections (of any kind) hit me hard, sometimes they don't; sometimes I feel anxiety prior to an approach, sometimes I don't, and so on. I don't think I have reached my full potential, and one major sticking point for me is not giving a shit.

I've read books, articles and advices, and they all say "don't give a shit." But how do I actually not give a shit?

Simply deciding not to give a shit doesn't seem to be enough for me, as the give-some-shit negative thoughts would keep coming back and my brain/emotions would buy into that.

For example, a woman probably misheard what I said in one of today's approach and she almost took it as an offense (she stopped smiling, came closer to me in a rather threatening way, and said "I'm sorry, what did you just say?" -- and I was somewhat scared at this point). After calmly repeating what I said, however, things went back to normal. So I decided to not give a shit about that. But then thoughts like "You almost offended her! Bad things could have happened! Better be careful next time!" kept coming back. As a result, I would slip back into giving too much shit despite my conscious effort to stop it.

Trying to replace such negativity with positive thoughts (e.g. "If my compliment or non-offensive remarks offended her it isn't my problem, it's hers, so I don't care how she responded") hasn't worked very well either. It just seems like some parts of my brain just refuse to not give a shit, maybe I'm missing something here.

tl;dr How do I actually "not give a shit"?