Why do we age? genetics v lifestyle

Not sure if I've made this point clear before so here goes. As I see things there's a strong possibility that aging and its symptoms could be largely related to levels of activity and the balance it has with nutrition and recovery.

The link I see is that old age is linked with both reduced activity and reduced levels of human growth hormone (HGH). HGH encourages cell maintenance as well as growth. Now there's no evidence that aging reduces potential for exercise. It lowers your maximum marathon speed but doesn't stop you running a marathon. 

Your capacity for exercise is directly related to your regular participation in it and the quality you put in. So is it any surprise that we're less active as we age so we lose the capacity for quality activity. Concomitantly we don't encourage the production of HGH and our bodies wither like a flower with no sun or rain.

Children on the other hand are generally the healthiest. Their attitudes are to be admired. The take big challenges in their stride they take failure as something normal and something to over come. They don't worry about tiredness or activity they just play and rest play and rest. They're more in tune with their bodies . This shows in their lifestyles and their health. 

As we age we seem to lose touch with our bodies we don't work as one with them we work against each other so neither actually achieves its goals. I'm learning how to work better with my body and find out what it can do with some TLC and respect. Already I feel younger. I'll see
how this works in time