Because of the emphasis on inspiration, self-examination and the making of new resolutions common at farbrengens, they are also often held in preparation for events related to teshuvah, such as on Thursday (in preparation for the Shabbos, whose letters השבת can be rearranged to spell teshuvah, תשבה), Rosh Chodesh (which has similar qualities to Rosh HaShanah and Yom Kippur), or similar days.
The reason for the l'chaim is to open the hearts of the participants to be inspired to want to change, and internalize what is being spoken at the farbrengen.
In addition, since the farbrengen often includes discussion about very sensitive matters, with pointed criticism, alcohol is consumed in order to lessen the tension amongst the participants.
However, it is only meant to be drunk sparingly, as Rabbi Menachem Mendel Schneerson forbade drinking more than four shot glasses of alcohol ("l'chaims") for anyone under the age of 40.
This power stems from the idea that when God, regarded as our father, sees that His children are sitting together in unity and love, He is then aroused with a desire to fulfill all their requests, even those of which they would not be worthy via normal means, such as via the advocacy of Michoel, the defending angel of the Jewish people.
Indeed, Chasidic tradition includes many stories of people who were saved by taking part in a farbrengen and being thereby blessed.