A_A,

The older you get the more you realize that youth is truly wasted on the young ;)
Staying active as you say is the key, but it's also never to late to get in better shape and better overall health.

Since 75% of our health problems are lifestyle/diet related, adopting a better eating plan and just a daily walk and some stretching afterward will go a long ways.
Yoga is an excellent way to keep strong and limber and proves you don't need to beat your body into shape to get in shape.

Biggest drawback to entering Geezer-Land when it comes to exercise is that you don't bounce back as fast from a hard workout.
When your new to exercising and especially if your older, you fall into the " no pain/ no gain" trap.
There's a big and very important difference between physical fatigue and real pain.
People of all ages, especially older ones need to ease into an exercise routine and make stretching afterward as much of a priority as the exercise itself.

More people start and stop exercise programs becasue they try to keep up with the " Jones" in the gym, rather than listening to their bodies. Once hurt they more often than not, decide exercise isn't for them :(

There's something for everyone, you just need to find it.