Exercise, eating healthy, good sleep, meditation etc. All things which are obviously beneficial after the act, yet difficult to bring about. Why is there any resistance at all?
Because the things that are good for us that are easy to do, we don't have any problem doing, so we don't think of them as "good for you". Instead, we think of them as "stuff I like to do".
Historically you had no choice. You had to exercise to get food and veggies and small quantities of sugar were all that was available. The sun going down kind of limited what you could do.