"Youth is like ...."

Youth is like spring, an over praised season more remarkable for biting winds than genial breezes. Autumn is the mellower season, and what we lose in flowers we more than gain in fruits.

Samuel Butler

"... I believe an authentic old man ...."

… I believe an authentic old man would be honest with himself about how much fully conscious and rational life he has left.  He would want to use that time in the best and most appropriate way.  I also suspect he might sense that this stage of life offers meaningful possibilities that were never before available to him.

Daniel Klein