Oh, one of the secret-keeping quotes that gets repeated all over the place because it's one of his witty retorts was when he first came to the throne, was planning something (now known to be the invasion of Silesia), and everyone wanted to know if there was going to be a war and where and when.

When one courtier was trying to winkle the truth out of him, Friedrich beckoned him over and took him by the hand. "Can you keep a secret?" he asked, sotto voce.

"Oh, yes, Your Majesty." The guy started to get excited.

"Well, so can I!"

Fritz was a first-rate troll, all his life.

But of course, reading that, all I can think is, "Yes, you learned that the hard way, and then never unlearned it. SOMEBODY GET THIS MAN A THERAPIST!"