What she does and who she sees,
She can do whatever she please.
But inside it hurts, I'm feeling pain!
To think of them learning to love again.
How selfish am I, for I've moved past,
A new girl has my love at last.
Perhaps one day it just won't matter,
And once again we'll freely natter.

Moya Levy

http://www.poemhunter.com/poem/0014-why-do-i-care/