Investing time in a marriage, or parenting, or working out seems less important than just about anything at the moment you have the opportunity to do it, but lots of people get divorced and it makes them very unhappy. Lots of people are estranged from their children and it makes them very unhappy. Lots of people suffer from health problems directly related to diet and exercise.
Obviously there are lots of things we can't control and I certainly don't mean to suggest that anyone who gets divorced, etc. brought it on themselves, but for how mundane most people consider these things, becoming a fit, healthy 60 year old who is happily married to a wife of multiple decades with fulfilled adult children is really quite exceptional. I think that would fit most people's idea of a "great" outcome, but in my experience, people don't really strive toward that on a daily basis, because the daily building blocks don't seem important.
From what I've seen as an attorney and tax accountant, greatness in a profession is also more closely related to getting the little things right day after day than any sort of heroic undertaking. There's always a place for heroics, but I think most people would be surprised at how often the little things get messed up, and how easy it is to look quite competent by just doing the seemingly mundane things consistently.
I feel the complete opposite. The only reason I do the other things is so I can be good at those 3 things (and a few others in a similar category).