Emotions such as anger, resentment, envy, and bitterness tend to undermine happy social relations. But the virtue of gratitude is not only a firewall of protection against such corruption of relationships; it also contributes positively to friendship and civility, because it is both benevolent (wishing the benefactor well) and just (giving the benefactor his due). In gratitude, we show our respect for others by recognizing their good intentions in helping us. A grateful outlook can even dominate the life of an entire culture, as can be seen in certain Eastern cultures where individuals view themselves as recipients of endless ancestrally bestowed blessings.
— Robert A. Emmons, Thanks! How the New Science of Gratitude Can Make You Happier