It can't be that, I think, because of the length and the two question-marks.
It rather looks like it could be Gandalf to Bilbo, right at the end of the book:
"and why should not they prove true? Surely you don't disbelieve the prophecies because you had a hand in bringing them about yourself? You don't really suppose, do you, that all your adventures and escapes were managed by mere good luck, just for your sole benefit?"
Although "mere good luck" is not right at the end of the sentence...
