The exercise was to take a favorite poem (by another author), delete every second line, and replace it with something you wrote. After that, you go back and replace the lines you left the first time, and what you end up with is an original poem.
I chose Vespers by A. A. Milne. I love the image of the little boy trying to focus but not quite succeeding. This is what I ended up with:
Hide & Seek
He crawls under the covers to the foot of the bed.
It’s time to be sleeping; he’s playing instead.
Quiet now, like he’s saying his prayers.
Here is Mommy, coming upstairs!
She’s out in the hall, turning off the light.
Is she coming in here to say goodnight?
She’ll never see me. I won’t get caught.
Hide and go seek! Ready or not!
Here it comes now, what I’m waiting for:
I hear Mommy come through my door.
She thinks I did what she said I should.
She won’t find me here, though; I’m too good!
She’ll never guess that I’m hiding in bed.
I’ll keep the blankets up over my head,
And I’ll shut my eyes, and I’ll curl up small.
She won’t see me. Not at all!
Mommy says now that it’s not time to play.
She thinks that I’m trying to run away!
She’s going back out. She didn’t see!
I’m silent and still and she’ll never find me.
Under the covers at the foot of the bed,
Soundless, unmoving, dozing instead.
Mommy picks him up and tucks him in right
And smooths his hair, and whispers “Good night.”