From Wicked musical, Glinda sings to Elphaba (For Good):
I've heard it said
That people come into our lives for a reason
Bringing something we must learn
And we are led
To those who help us most to grow
If we let them
And we help them in return
Well, I don't know if I believe that's true
But I know I'm who I am today
Because I knew you...
Like a comet pulled from orbit
As it passes a sun
Like a stream that meets a boulder
Halfway through the wood
Who can say if I've been changed for the better?
But because I knew you
I have been changed for good
