Getting better with age?

When I was in my late teens, I was in pretty good shape. I was on the high school track team, tennis team and grass hockey team. I also did some bodybuilding and even worked at Gold's Gym for several years. In my 20's I worked in offices and believed I could climb the corporate ladder. I gave up fitness and spent my days working overtime and on weekends and traveling for work for extended periods of time. I lost all that muscle definition I had in my teens and even went to doctors for sore knees and back. I couldn't wash my face without holding onto the counter, and bending over to brush my teeth also hurt. I was quite thin because I never had time to eat. I lived on several cups of coffee and some cigarettes.

In my early 30's I experienced three significant life changing situations and lost who I was. I gained weight and had trouble going up and down stairs - we'd take the elevator at the shopping mall because my knees hurt so much.

But by the end of my 30's things changed - I got myself together. I regularly did pilates and then yoga, and then I started dancing. And once I got a labrador puppy I committed to walking every day  - every day except if one of us is hurt or injured.

Now I feel like I am in really good shape. I'm not skinny but I'm healthy. I have energy. I feel strong. I can run up and down stairs without knee pain, my back rarely hurts (usually only following something silly in the garden).

And minor issues seem to have subsided as well - I was diagnosed with a heel spur and was told it would never go away. I bought orthotics and wore them daily for a year. Now I only wear them during my dog walks and don't feel that pain.  And, for years I suffered with sore throats and mouth ulcers. A diagnosis told me that they were caused by a reaction to things I've eaten - not an allergy, so not to bother with allergy pills for this symptom. I decided I'd notice the pain but I would also ignore it. And also not bacterial. I haven't gone to the doctor or antibiotics for my throat in several years.

I thought the best health in our lives was our twenties, but for me it seems like now is pretty good. Is that what they mean by middle age? Am I at my peak now and will I decline from here on out?

There are lots of inspirational stories on the internet about people that are in fantastic shape and going strong in their 70s and 80s and even nineties. Can we get better with age? If we put our minds to it, how much control do we really  have? If we don't go 'overboard' and wear ourselves out how much illness can we prevent?  What do you think?