As someone is less than a couple of years away from a free statewide mass transit pass, I can't stress physical fitness enough. The body you have now is the one that will be carrying you through old age. Get it in shape for the long haul! No one is living life fully if they are obese and have mobility issues. No one is living life fully if they are wracked with pain every time they move around. Walk, bike, run, go to the gym, do yoga, play tennis, take the stairs, but do something. Your physical activity will affect your weight, your sleep, your appettite, your attitude, your appearance, and so much more. If you start getting into shape it's going to be tough, but then it gets easier until you really look forward to your excercise every day because you are going to absolutely crush it. As you lose weight and get stronger you will quite literally feel younger. Crappy, delicious, calorie laden foods? Go for it if you burn 'em up.

And yes, as you get older you do become invisible. A way to stay connected to young people is to do something that they like to do. I'm a bicyclist, and it truly is a massive informal worldwide community of every kind of person imaginable that just really likes bicycles. If I'm riding with a group of youngsters (And keeping up!), I feel as young as they are. It's magical, and then afterwards I have a Red Velvet milkshake with no guilt whatsoever, and that is magical too.