'Discounting' is what the professionals call a 'psychic defence mechanism against other people's success'. It's what you unconsciously think when your friend gets the promotion ('Big deal, he may now have the corner office and the car, but have you seen his wife? She's a dog!') or when a university peer is suddenly nominated for the Booker prize and gets a pounds 100k advance from a publisher ('Yes, but he lives in Slough, and he's got acne').
Putting down, dismissing and rationalising other people's success to make oneself feel better is one of the few conditions that psychiatrists don't try to cure because it's considered rather healthy. You start to worry when news of an ex-employee's IPO for pounds 40 million is met with huge grins and applause. Then you know something nasty's up.