I'm surprised no one has mentioned Fable from The Light in the Piazza yet. Here are some others:
Anytime (I Am There) from Elegies: A Song Cycle
The Story Goes on from Baby
And Eve Was Weak & I Remember How Those Boys Could Dance from Carrie (definitely a different kind of mother/daughter song, but still)
"You travel alone because other people are only there to remind you how much that hook hurts that we all bit down on. Wait for that one day we can bite free and get back out there in space where we belong, sail back over water, over skies, into space, the hook finally out of our mouths and we wander back out there in space spawning to other planets never to return hurrah to earth and we'll look back and can't even see these lives here anymore. Only the taste of blood to remind us we ever existed. The earth is small. We're gone. We're dead. We're safe."
-John Guare, Landscape of the Body