‘You see, sir,’ said Willikins, ‘being definite is what gave them all this money and land. Sometimes lost it for them as well, of course. One of Lady Sybil’s great-uncles once lost a villa and two thousand acres of prime farmland by being definite in believing that a cloakroom ticket could beat three aces. He was killed in the duel that followed, but at least he was definitely dead.’

[...]

'He never worried about who he was. He was a decent old boy, her father – and her granddad, too. Certain, you see, never worried.’

They walked along an avenue of chestnut trees for a while and then Vimes said, morosely, ‘Are you saying that I don’t know who I am?’

[...]

'As for your question,’ he went on, ‘I think Sam Vimes is at his best when he’s confident that he’s Sam Vimes.’

— Snuff by Terry Pratchett (10%)