I really don't know what your mind is supposed to feel like as you age. I know I'm mature in my behavior and one thing that's nice is you start to care less about what others think. It's freeing in that sense. I have a 9 year old Daughter and a 10 year old Son, I have a lot of fun with them. The biggest bummer about aging is your body starts to she it's limits. For example I can't spin my Daughter around because I get very dizzy. I am going through some changes that come with age and that's not always easy either.
But you know I'm thankful for my health and the ability to function normally. I try not to think about the number, just the good fortune of being alive and healthy.