And so it annoys the shit out of me that when a friend in finance got a $10k raise, all she could talk about was "but I lose half of it to the government!". In some strange world where 30% equals half, she's more concerned about what she lost than the fact that her gain was almost equal to a poor person's annual income. She couldn't even frame her payrise as a positive.
There's more to life than feeling lucky we aren't in bad situations. I'd say ambition is more useful. A million dollars at 4% interest accrues $40k/yr, so in effect any millionaire is given 4x her raise every year just by doing nothing.
That's not a bad thing. It's just a fact of life. But "you should be happy with what you have" is practically a recipe for sabotaging your ambition.