Cicero once said, “Gratitude is the greatest of virtues, and the parent of all the others.”
Sit back and think on the second half of his maxim for a moment: can any other virtue truly exist without gratitude? Is hope truly hope without gratitude for that hope? Is humility sincere without gratitude for what one already has? Can justice be had without gratitude for the opportunity for that justice? Can respect be sincere without the appreciation of how that respect has been earned, and can that appreciation be truly felt without gratitude for being able to recognize that appreciation?
That last one may be somewhat more convoluted than the first three, but Cicero’s principle still holds: without gratitude, all other virtues are lessened, made hollow, or even nullified. You extol the virtues of hope and courage, but is hope real without the appreciation for what that hope can bring? Is courage real without appreciation for what courage really is, and what that courage demands? And what is appreciation without gratitude?
Happiness, then, cannot be had without gratitude. Gratitude in all things (or at least as much as possible) is the key, even for the poorest of people (a link to the homeless I knew in the Philippines).
Conversely, look at those who are unhappiest. There will be exceptions (such as those who have borne great tragedies), but generally speaking, those who are unhappy are those who are not sincerely grateful for what they have, whether they have much or little. They have not learned to count their blessings.
I no longer follow the same religion as my mother did (she was Southern Baptist, I am part of the Church of Christ), but there was a hymn that said much the same thing: “Count your many blessings, name them one by one. Count your many blessings, see what God has done.”
Gratitude is the key.