I easily adhere to proper eating and exercise.

Adherence is mostly a property of the kitchen rather than the character. What sits at eye level in the fridge, what is already chopped, whether the walking shoes are by the door or in a box under the stairs.

People who manage it consistently rarely have more resolve than anybody else. They have arranged things so the default option is the one they wanted, which means the decision only had to be made once, on a Sunday, instead of fourteen times a week while tired.