If your live style and attitudes brought you to the point where it takes willpower just to survive or socialize, I'm not sure it'll help you to think of things like making a sandwich as some kind of all-out effort.
If I had to give a suggestion, it would be to focus your willpower on grander ideas than just outright survival or self-pleasure. Engaging in things like self-improvement, community service, learning new skills, or setting up large projects would make day-to-day stuff a lot less of a hassle because things like eating sandwiches or taking showers would then serve a purpose in your mind worthy of said hassle.