Such a good thread. I love hearing your ideas.
I too have a list of birth mantras (affirmations?) that are my favorites. I use them in the weeks leading up to labor, when I begin feeling the fear and nervousness of the impending pain and work that labor is. They include several things you guys have listed, about softening & opening and my body being made for this. All sorts of sweet things that remind me how natural and good labor is. However, I've learned that during labor, all those sweet "open, soft, gentle mouth, etc." sort of mantras do nothing for me! LOL In my experience I do not find hard labor in any way to be soft and gentle and I am FAR from being able to relax my mouth. I had one labor in which a bit down on a pillow so hard for so long I could barely chew for the next day. LOL
There just happen to be 2 things that have appeared in my brain over my years of baby having that have really worked for me and stuck with me during the hardest part of labor. They are "the only way out is through", and "it's okay...it's good.....it's okay......it's good". I chant & chant these things in my mind over & over. The first one came to me years ago during transition or the early pushing stage, when I was right on that cliff of panic. I was feeling those creeping negative thoughts starting to come to me, such as "I can't do this, I'm scared to death" etc. Then I remembered- I'd done this before. I knew, "the only way out is through!! JUST PUSH!" And I did, chanting that thought the whole time. And it's true, the only way OUT of all that pain IS through. Ya just push through it and before you know it, that warm tiny perfect baby is in your arms.
The 2nd chant is just a reminder to me, that all of this pain & work IS good, it IS okay. Those words help keep the negative words away. I can't be chanting "it hurts, I can't stand it" when my brain is full to the brim with "it's good, it's good, it's good". It IS good! The baby is coming!