I think the best way to avoid self-control fatigue is probably to automate as much as possible and make the correct option the easiest one. Like, finances can be close to 100% automated and require zero effort. You can even set up things like an automated weekly grocery delivery these days (I used to do it when I was single). Weekend meal prep ensures you have zero-thought, zero-effort meals all week. People have long found that not keeping junk food at home usually almost entirely eliminates consuming it, because they eat what they do have instead rather than going to the effort of going and buying potato chips. Being very minimalist and living in a small space greatly reduces daily housework. Not having a car at all means you don't need to have an internal struggle between biking or driving somewhere. And so on.
Many years ago I decided I wanted the vast majority of my non-working time and mental energy to go towards fun things instead of boring shit, so I implemented all of those things, and it really does work.