I think they ought to know. You do them a disservice by not confiding something this important to them.”
“I didn’t want —”
“— to worry or frighten them?” said Dumbledore, surveying Harry over the top of his half-moon spectacles. “Or perhaps, to confess that you yourself are worried and frightened? You need your friends, Harry. As you so rightly said, Sirius would not have wanted you to shut yourself away.

Author: J.K. Rowling