I know most people feel the opposite, that their weight or their skinny arms or sagging butts are the one thing they'll never be able to control. I've been there, too. Three years ago I relocated back home to LA after living in NY, and all the stress of moving and finding a new career made me blow up like a balloon. At your age, you're not going to look the same as you did when you were twenty. That's all I had to hear, and I was on the stairmaster and treadmill.
Exercise is like the opposite of a vicious cycle.
If you stick to it, you see the results, which makes you want to stick to it more, and soon you enjoy what started out as drudgery and punishment. Then more results, then you like it even more. Before you know it, a way of life is born. I'm not a kid, nor a steroid freak. I'm a well-muscled, attractive grown man.