Automate all the things. The more you have automated, the more you can focus on the actual problems and tasks. You may not get any more total work done (by an hours perspective), but your total labor will be much more effective.

Record all the tasks you need to do, prioritize and track them. Once they're out of your head, like with automation, you're doing more with less. Your mind can focus on the present and not the future, or the past by second-guessing (did I finish X?). I find that being more "present" (in this sense) keeps my motivation going.

Regarding sleepiness, I found that eliminating sodas (as a source of caffeine, still have caffeine but in a twice-a-day cup of espresso and yerba mate) greatly reduced my afternoon sleepiness. Along with general improvements to fitness (running, soccer, BJJ, bodyweight strength/conditioning classes, in my case). Being fitter (less excess fat on my body, able to run for an hour or more without exhaustion) has led to better wakefulness throughout the day (this is a process, initially I was much more tired for the first month or so).