I am 23. I am young and healthy. I realized today that I better damn well take advantage of this. I don't want to look back 30 years from now and wish I took advantage of my body and ability to get in better shape. I know that doing triathlons (or any athletic endeavor) will not get easier the older I get. Running will only come with more aches and pains, and biking will only hurt my back more. I'll only get slower at swimming.
Yes, there are those later-middle aged folks who are amazingly fit and active. However, this is the last time in my life I have all the time in the world for myself. All I have to balance right now revolves around the world of Jayme. School, job, dog, boyfriend. All Jayme-centric. Once I get married,have kids, I have a feeling that things will move from more Jayme-centric to kid-centric and family-centric. So instead of trying to juggle the potential that comes with this amazing body I have been given with work, kids, family, *other people!*; I am going to take advantage of it NOW.
On the plus side, If I take care of myself now, it'll pay off later. I've never heard anyone regret eating healthy in their 20's or staying active.