A Big One!

I've never had such a big one
I'm surprised it even went in,
For a moment it stuck in the entrance
But with greasing we managed to win.
With eyes open with anticipation
I gathered myself for the charge,
For I've never seen anything like it
And taken nothing so large!
You were determined to get it in there
Of that I had no doubt,
But as fast as you pushed it forward
My muscles were pushing it out.
Too late I saw my mistake here
For now it's become quite small
And although you can get it in now,
It's no fucking use at all!