[Gratitude] is the recognition that the good in our life can come from something that is outside us and outside our control—be it other people, nature, or a higher power—and that owes little or nothing to us.
In paying homage to something that is outside us, gratitude enables us to connect with something that is not only larger than ourselves but also fundamentally good and reassuring. It opens our eyes to the miracle that is life, something to marvel at, revel in, and celebrate, rather than ignore or take for granted as it flies us by. It encourages and heightens life-enhancing states such as joy, tranquility, consciousness, enthusiasm, and empathy, while inhibiting painful emotions such as anxiety, heartbreak, loneliness, regret, and envy, with which it is fundamentally incompatible.Psychology Today
For more, see The Psychology Of Gratitude.