Concentration with trying to find the joyful parts of the breath and move focus to those as much as possible. I'm nearly convinced I want to stay in concentration practice until I reach the first jhana. I tried the 1..10 out-breath counting during the day some and it's really friggin' hard while talking to people.
At one point during the day I told my PM ~"Don't come to a conclusion then figure out why it's certainly right. That's the wrong way around." This was mildly socially inappropriate (though we were alone so it wasn't hugely bad) which was probably fine except I didn't think it all the way through before speaking.
I went back over my quick Fermi calculations for whether buying a car is worth it and found one glaring math error and one glaring structural error. The math error was a completely dropped term which was in favor of buying a car, and the structural error was that I looked at the one-year benefits, not the one-time benefits minus costs plus the per-year benefits minus costs. Fixing the structure is also in favor of buying the car. Translating to dollars it looks like even buying outright gives about a 100% ROI capped at a $15,000 investment with a bonus $5,000 one-time gain, and that's without a loan. (note: those numbers aren't real 'cause some of the costs and benefits aren't dollars and unlike dollars can't scale up)
Then I tried to go back over my pen-and-paper estimate I did near the beginning of mini-camp of "would meditation bring me significant benefits?" and see what it looked like when I drew the full causal diagram of how the pieces of evidence I had brainstormed connected, then compare that math with the sketchy math I did to estimate. I got stuck when the undirected version of my causal graph had loops. This session was definitely evidence in favor of "Don't Try to Practice What You Don't Yet Know".
Frustrated, I decided to end with a couple Wits & Wagers cards 50%/90% calibration and call it a day. I got 4/14 and 8/14, so I'll be doing calibration exercises next time for sure.