Aging is not 'lost youth', but a new stage of opportunity and strength. It's a different stage of life, and if you are going to pretend it's youth, you are going to miss it. You are going to miss the surprises, the possibilities, and the evolution that we are just beginning to know about because there are no role models, no guideposts, and no signs.
This is a nice thought, but not really true of the actual experience of aging. The death of youth is horrendous, and we all mourn it in different ways. Pretending it's ok that our youth is gone is just something we say to make ourselves feel better. Just like those with no money often tell themselves money doesn't matter. Deep down we know we are lying to ourselves.