This is a very individual topic so I'm not sure how relevant my advice will be to others here, but I'll try.

I don't play marathon sessions because I know after about 4 hours the quality of my play drops and I start to develop severe back pain. I mostly play with a standing desk for this reason. There may be the rare fish that I would keep playing against, but in most cases I'm done after that. It costs some EV in the short term, but if I wreck myself on Monday and need to take Tuesday off, that's usually a greater EV loss. The other way to think about it is that every time you quit a reg you're beating, you are advertising, convincing them they can win so being the guy who never quits can actually hurt you in the long run.

For your next question: Meditation helps. I also will run a 5k in the gym or a mile at top speed when I feel the lingering tilt energy from my session in my body. After that, I find my body is tired, but my mind is fresh.

microsoft excel and the solver and brute force. I've made probably over 3000 of these for every line and stack size in the game tree

there is only one 5c solver. It's private and companies like RIO and Jnandez bought a copy and use it to create their sims. I've got my own copy as well