I don't know how to break down all the stages of life.
My favorite part was during the middle years, 30-50 - a family, a career, a full life, vacations. After that came more careful planning for retirement, but that did not go as hoped for in my case, due to the loss of my wife.
In recent years, I often feel I'm just sort of drifting, but still thankful for decent health, and there are still good days.
In my mind, the final stage will be when / if I'm stricken with a serious illness, and it does me no good to think on that, so I generally don't.