We retire too early and we die too young, our prime of life should be in the 70's and old age should not come until we are almost 100.
Physical fitness is the first requisite of happiness. In order to achieve happiness, it is imperative to gain mastery of your body. If at the age of 30 you are stiff and out of shape, you are old. If at 60 you are supple and strong then you are young.