Marking

I've spent my life just marking time
10 out of 10, so it's been just fine.
The older I get, the younger I feel
Life goes round like a Ferris Wheel.
It's all a bit scary when you get to the top
And when you're there all you see is the drop,
But I'm on my way down the other side
And truth be told, I've enjoyed the ride
And the view's quite good as you're going down
And I'm not worried about hitting the ground
'Cos when I reach three score and ten
I think I'm going round again!