I think this is quite good advice for us, as we handle our children's questions about their birth families and circumstances.
'The truth.' Dumbledore sighed. 'It is a beautiful and terrible thing, and should be treated with great caution. However, I shall answer your questions unless I have a very good reason not to, in which case I beg you'll forgive me. I shall not, of course, lie.'
And this is just plain good advice for everyday life.
'There are all kind of courage,' said Dumbledore, smiling. 'It takes a great deal of courage to stand up to our enemies, but just as much to stand up to our friends.'