זה היום עשה ה' נגילה ונשמחה בו

If "Zeh hayom asah Hashem" - you realize that today is a gift from Hashem, "nagilah vi'nismaicha bo" - then you will rejoice in Him. But if you take today for granted - simcha will elude you....

[Rav Yechezkel Weinfeld Shlita]