What is your “apple a day?”
Yoga has never really been my thing, despite many years of practice, I never really attained flexibility, though I was certainly much more flexible than when I started.
I do quite literally have an apple a day (at least one, often 2 or three), and something between it and the heaped teaspoon of vitamin C means that my only trip to the doctors in the last 4 years, for other than checkup, has been for a broken collar bone.
Positive attitude, rest, exercise (golf is my preferred form), and walking or cycling are enjoyable.
Belief in self is probably right up there, as is doing something in service of others.