TL:DR Tried to negotiate anal sex, failed, then stuck to RP principles and profited

Context: Been working on MRP for ~3 months, I'm 38 years old in a new LTR

Two days ago I made the mistake of trying to negotiate anal sex with my girlfriend of almost a year. Stupid me, I got the inevitable hard no, and a long thing about how she doesn't want to do that again because of blah blah blah... and I felt myself getting butthurt and angry. I lost frame and before I went off the rails, I stopped myself and told her that if anal sex is forever off the table, that we have a problem. Then I STFU and left for the gym, told her to be ready in 45 mins for a family visit we'd planned.

When I got back she wasn't ready, and when she was 15 mins late I said goodbye and that I was leaving. I have been working on my integrity around being punctual so this is a non negotiable. She rushed to meet me at the car before I left and we had a fight that was mostly due to me losing frame and still being pissed about the anal thing. She called me on that too. I held it together somewhat telling her that part "hadn't helped" but that I will not let her make me late anymore and I will leave on time with or without her. I ignored her for the first part of our drive and called a couple friends to make arrangements for Christmas events, then went back to talking and joking with her about other things. We end up having a fun day and later that night I drop her at the subway so she can meet two of her girlfriends for dinner. That night we fuck hard and I cum early because I want to get to sleep. She tells me she is still horny and can we fuck again. I tell her I'll fuck her ass, she says no thanks, and I say goodnight and go to sleep.

Next afternoon we're initiating and she tells me she'd like to try anal sex. I take it in stride, joke that I've told her before she can't peg me with a strap on. Then I get the lube and we get down to it. After some trial and error, we finally get into comfortable anal sex and it was FANTASTIC. She high fived me when I came in her and she had her own orgasm from playing with her clit. Later she apologized for saying she didn't want to do anal the day before, and hamstered that she just wanted to make sure it was fun for both of us.

BP me would have shot myself in my own foot by losing frame completely on this. Hell, I am still very BP internally. I was starting to talk myself into accepting a life with no anal sex in it, because of how good everything else is with her. Then mid work out I decided that wasn't going to be good enough, and that one way or another I'd have every thing I wanted in my sex life no matter what. To be balls deep in her ass a day later, high fiving was nothing short of a miraculous turn around for me. Doing STFU and pretending IDGAF was hard and I didn't really do it perfectly but the result was perfect none the less.