The Emotionally Painful Process of Growing Up

I've heard many friends, peers, relatives etc. say their childhood years were their golden years. Including myself, I'll admit. Growing up is inevitable no doubt; but why is it that when we see that one person of our own age group that is as reckless, jolly and happy as a 5 year old, we feel instantly connected to them? These carefree ones seem to force ourselves to think about our own attitude in life.