There's a recurring truth in my life: "keep it simple stupid." I first encountered this phrase early in my programming career. My mentor, a greybeard whom I still admire and keep in touch with, shared this tidbit of wisdom when I proposed some fluffy, over-complicated solution to a problem-- as young folks who are looking to prove themselves are wont to do.
I don't recall much about that specific problem and its solution, but the principle has stuck with me, hammered into my psyche by years of experimentation where I tested the "simplicity" hypothesis.
This principle doesn't apply to only engineering problems. I've known it to be a truth in almost all facets of my life.
For exercise, keeping detailed data gave way to just putting on my running shoes in the morning and doing it.
For creativity, I've found that regular practice will lock me into the flow state more than any hand-wringing about tools and techniques ever has.
For diet, keeping a pantry stocked with healthy foods makes it easy for me to eat well.
For sleep, I've found that a regular schedule with activity in the morning & afternoon and rest in the evening makes falling asleep easier.
Chuang Tzu once wrote, "when the shoe fits, the foot is forgotten."
Sometimes it takes a while to find a shoe that fits. Simplicity, for me, is knowing not to go shopping for shoes when your feet are comfortable. :)