Because gratitude is the key to happiness, anything that undermines gratitude must undermine happiness. And nothing undermines gratitude as much as expectations. There is an inverse relationship between expectations and gratitude: The more expectations you have, the less gratitude you will have.
Of all the characteristics needed for both a happy and morally decent life, none surpasses gratitude. Grateful people are happier, and grateful people are more morally decent.
Happiness is impossible without gratitude.
Given the amount of unjust suffering and unhappiness in the world, I am deeply grateful for, sometimes even perplexed by, how much misery I have been spared.
