The quote was from the biography of Howard Thurman.

http://books.google.com/books?id=Z5_07RsCWWsC&pg=PA97&lpg=PA97&dq=black+girls+on+a+swing+this+is+how+important+you+are.&source=bl&ots=ACeNcnItjm&sig=ArQo7ToNAcsjiMZIPtscObYJhUo&hl=en&sa=X&ei=1jogT5z7MYWtiQKm39HPCw&ved=0CB8Q6AEwAA