You don't love me, but ah! do I love you!

You don't love me, but ah! do I love you!
It kills me that right now you have another!
Each day I watch the antics of you two
Happy hopping birds and say, why bother?
But I am chained to you as fish to sea,
Or as the moon to Earth, or Earth to sun.
The thought of letting go so tortures me
That I would rather let my anguish run.
I know that if I wait you will be mine.
Such love as this must sweep all walls away!
I am your natural light, and I will shine
Till due rotation turns your night to day.
Until then, this sorrow will remain:
My hope of joy must be my source of pain.