I don't begin to battle your heat (I simply couldn't live in that environment), but when I find myself overwhelmed, I try to get out for short spurts, with a goal of perhaps a 3' swath, or whatever is manageable for you to easily tend. Maybe it's just one wheelbarrow full. Something easily attained. Immediate gratification and slow steady progress. I also follow the shade, and think nothing of simply moving spots when the sun hits me.
I'm also a big fan of just sitting and staring at one garden to see what is working, what is not, and note changes to make in the fall or spring. They don't always get done, but it's nice to get a nice crisp fall day, open my Garden Ideas notebook and make a couple changes here and there.
Good luck with your mojo.
