An interesting topic..
Myself, I don't feel or act my age at all, in fact, I seem to have a case of 'arrested development' that started in my late teens/early 20's.. I see myself as about 20 - just managed to squeeze a whole lot of living in to that time.. I have a friend who is 17, and whilst she claims to feel a lot older than that, she and I mesh mentally and emotionally quite well..