TJ is right - it is mostly attitude and activity - or lack of it. What's 'middle age' anyway? To know you're middle aged surely requires that you know how old you'll be when you die. It's just an attitude, which some of us haven't got. And in the phrase 'acting your age', surely the significant word here is 'acting'. Why pretend?
Richard: responsible adult? I don't think anybody's levelled that accusation at me. I always thought grown-ups were boring, and never wanted to be one. And I haven't.
Valmai: perhaps you are getting up/going to bed at the wrong times; try getting up at the time you feel 17 and ....I'll shut the door on me way out shall I?
John Kelly.