I'm pleased to see that a recent survey shows that people do not believe themselves to be middle-aged until the age of 55. You can see the article over on the BBC website, here.
I believe that age is what you want to make of it - you're as young or as old as you feel. I'm bouncy and jolly (most of the time); I like to skip around the house and dance in the kitchen when I'm cooking the meals.
I intend to remain a Spring chicken for as long as I can.
Enjoy every moment - and have a great day.