I have to say my 50's were some of my best years.

My kids were late teenagers and pretty good company without tieing us down as much. Work was ok, as ok as it ever is anyway. Physically I was great, my older daughter got me into running 5k's, I skied and skated in the winter and was way more active than in my 40s when i was busier with work and youngsters. Hey, I got my first new bike in 30 years when I was 55.