I believe the Vonnegut quote you're thinking of comes from his letter to Xavier High School students.
He asks the students to create something, anything, and then to destroy it and scatter the bits of it.
He then drops this line,
"You will find that you have already been gloriously rewarded for your poem. You have experienced becoming, learned a lot more about what's inside you, and you have made your soul grow."
I believe the Vonnegut quote you're thinking of comes from his letter to Xavier High School students.
He asks the students to create something, anything, and then to destroy it and scatter the bits of it.
He then drops this line,
"You will find that you have already been gloriously rewarded for your poem. You have experienced becoming, learned a lot more about what's inside you, and you have made your soul grow."