It's funny how when you get here (I'm 47) you realize what a bunch of BS all the age complaints are. You appreciate life so much more, and -- speaking for myself -- are as full of energy and ideas as ever.
Based on what I have seen of old people, people tend to become more of what they are so if you are generally a happy person, you should be more so as you get older.
Which means I will be terrible in my old age...