תלמוד בבלי מסכת פסחים דף קט עמוד א
תניא, רבי יהודה בן בתירא אומר: בזמן שבית המקדש קיים - אין שמחה אלא בבשר, שנאמר +דברים כז
וזבחת שלמים ואכלת שם ושמחת לפני ה' אלהיך. ועכשיו שאין בית המקדש קיים - אין שמחה אלא ביין, שנאמר
+תהלים קד+ ויין ישמח לבב אנוש
It was taught: R' Yehuda b. Beteira says. " While the Temple is standing, there
is no joy unless there is meat, as it says (Deut. 27) 'And you shall sacrifice
peace-offerings and eat them there, and you will be joyful before the Lord,
your God'. Now that the Temple is not standing, there is no joy without wine, as
it says (Psalms 104) ' And wine will rejoice the heart of man.'"
This beraita is oft-misquoted and rarely understood. Every meat-and-booze-loving yeshiva bachur can quote 'Ein simcha ella be-basar ve-yayin' - no joy without meat and wine. The passage as normally quoted doesn't exist in the Talmud. Aside from that, there's the whole dichotomy of the Temple times vs. non-Temple times, and the lingering question that this is a superficial view of joy - it's only possible through the vehicle of meat and/or wine?
Clearly, R' Yehuda is setting up two separate paradigms for joy.
One, represented by meat, is the joy in the participation of a good world. When everything is going as it should, when man can feel that morally, nationally, religiously he is not only leading a fulfilling life but that the possibility is there for a real utopia-like existence. Then one can experience the joy that being at peace (shlamim) with himself, with the world, with God, family, nation, etc., etc. It's the good life. It's deserved complasence.
The destruction of the Temple meant that this great experiment between God and the Jewish people had more or less failed. Hope persists that it can and will be resurrected, but until then, the trials and tribulations of an unjust and cruel world are the order of the day. Joy, if found at all, is in forgetting about that which is around you.
R' Yehuda is contrasting the joy of full participation in a constructive endeavor - symbolized by eating the meat of the shlamim, and the joy found in escaping from an imperfect world - symbolized by drinking. In truth, we experience a bit of both - the joy of accomplishment and the escapism from a world that still has so far to go.