If you can say this in your mid-30's and your parents are well, then chances are your 40's will be similar. At 45 and I can honestly say I have never been healthier mentally or physically. It's great! Other than presbyopia, which is easily corrected, and gray hairs, which takes <10 minutes a month for my barber to extract, I too have yet to notice any effects of aging.

Given that my 77 year old dad says the same, I may have hit the genetic lottery. I suspect he will just unexpectedly die one day while mowing the lawn, never having known what it is like to feel old.