The Apter Rav - the Ohaiv Yisroel writes that one of the reasons why we dress up in masquerade on Purim is to show that the miracle of Purim came from something that actually would have initially caused us much grief. This, says the Apter Rebbe, stresses that the greatest joy lies in the knowledge that the opposite result might very well have happened. It is a Minhag that brings us ever closer to the true Dveikus Bashem and Simcha that lies at the heart of what Purim is all about.
Let us, with this in mind, remember the words of the Nesivus Shalom regarding drinking on Purim. He writes that the word "wine" is absent in the formulation of the Shulchan Aruch. "Chayav adam libsumei bePuraya ad delo yada."
The reason is clear. We must become inebriated with the concept of Purim and not with wine. The concept of Purim is that Hashem is very close and that we can achieve remarkable D'vaikus B'Hashem at this time. No matter how distant we are - even if we are "Arur Haman" in terms of our general distance from Hashem- we can become, at this particular time of Purim, as close as Boruch Mordechai.
From an article on Vosizneias over here.