People believe that bodies wear out as they age, but that's wrong except for teeth and joints. These are also two areas where medical science is perfecting good replacements, so it’s possible to get the wrong impression.
You can’t wear out your eyes by excessive reading any more than you can wear out your nose by excessive smelling. You can speed up matters through bad habits such as allowing the sun to shine on your skin, but aging is built into your genes.
Evolution designed organisms to pass their genes on to future generations as efficiently as possible. After peak reproductive years – the 30s in humans -- evolution loses interest, and the performance of your incredibly complex metabolism declines. Efficient processes become less efficient. Things break. You don’t wear out; disease eventually kills you.
If you want encouraging news, it’s possible in theory to physically alter genes so that metabolism doesn’t peak at 30 but at 100 or 200 or never.
In fact, over the past decade biologists have developed ingenious techniques to manipulate DNA. I reviewed a good book on this called A Crack in Creation. Look it up on Amazon.
Nothing about vast life extension violates natural laws, so it’s probably inevitable, but you and I were born too soon.