I'm 38. I'm not really sure how to think about my age from a bipolar perspective other than to know I'm like an infant fumbling around at times.
In general though I tend to feel old or young depending on the nature of the activity. If I'm experiencing joy and being playful I feel young. I feel this a lot when I am with my kids. Other times when I am with them I am called upon to leverage my wisdom as a parent. This makes me feel older, but not in a bad way. There are also times when they plain wear me down and I feel old in a declining kind of way.
The same is true for my experiences with adults. There are times when I feel young and free and others when I feel seasoned and others when I feel left behind.
My body and my energy tends to flow with my mind. I am starting to feel aches and pains more regularly than when I was younger. However, in the right mindset I have all the energy I need to keep up with my young ones. Amytime I feel too old to do something I think about Jack LaLanne. That guy was ancient and still busting out chin ups like they were a walk in the park!