I believe the question then shifts towards something like: “How correlated are the behaviors of rating one’s willpower as high (or low) in surveys and rating one’s happiness as high (or low) in surveys?” And here, my intuition is that people who report higher willpower levels are motivated to perform behaviors which generally denote strength and confidence, such as reporting a high happiness score in a survey. And obviously, I believe the reverse will also apply.

In my view, this is an obvious and major problem with self-rating surveys. It has always shocked me how research which leverages self-reporting seems to ignore the social psychological context. I see such surveys as being akin to Facebook or Instagram posts. They are asking us, in effect, to report to the world how we are doing. I believe sophisticated measures need to also be applied to counteract the natural tendency of promoting oneself to the world, or at least, to try to measure the extent to which a person is biased towards exaggerating positive qualities, or downplaying problems. One possible approach would be to videotape each person as they fill out the survey, then show it to one or more others, and then survey the observers in a clever way to determine how motivated the original subject might be to project a positive image, vs being completely candid and being as accurate as possible.