I just went for the first thing that popped in to my mind that is a primary reward -- something biology has conditioned me to want, and will activate reward pat

I just went for the first thing that popped in to my mind that is a primary reward -- something biology has conditioned me to want, and will activate reward pathways (quickly!) when ingested/experienced. Honestly, you could probably just start with the secondary reward of congratulating yourself -- it's just important that you do it out loud and call yourself by name (eg, "John, you did a good job of running today"), so you hear it happening, instead of it being part of your mental dialog. Generally though, I find that speaking to myself is psychologically different than talking to myself internally, so YMMV if that's not true for you.