I have a simple choice every day now. If I excercise or be active I don't eat but a few snacks during the day. I get fitter, lose weight and my clothes fit again.
If I don't exercise or I'm not active I eat two to three times what I eat when I exercise or am active. I gain weight and my clothes become snug or don't fit.
So, it's a simple choice now which I do and who I want to be, healther and fitter or not. And when you're older, you can't give yourself too many days off from exercise or you find it harder to get the will to exercise.
I read once that your physical fitness habits when you're old are set in your mid-late 30's. You can change this but it's harder to get better and far easier to get worse. So, take heed to learn and do well in your 30's for it will pay off 20-30 years later, and you'll thank yourself.
Trust me, been there, done that and am there now.