It dawned on me the other day that in some languages like Portuguese, we use the same word for "Merry" and "Happy".
So with Christmas in the air, "Feliz Natal" in Portuguese or "Feliz Navidad" in Spanish could be "Merry Christmas" or "Happy Christmas".
There is an ongoing discussion of the difference between one or the other: why do people say "Happy Holidays" and "Merry Christmas"? The explanations can be found here.
But going through a dictionary defintion of the word, "merry" is synonymous with word like festive, joyous, gleeful, jolly, hilarious, laughingly happy.
Based on that, being merry has to do with external factors: a party, a celebration, a family gathering.
That's probably why we say "Eat, drink and be merry" and NOT "Eat, drink and be happy".
And I am guessing that's why it's easier to find the secret of being merry while there seems to be no one answer for the secret of being happy.
So: do you prefer a "Merry Christmas" or a "Happy Christmas"?