Adar is a very happy month, an auspicious time for the Jewish people, as we go from the Redemption of Purim to the Redemption of Passover. Redemption, however, including the destruction of Amalek and burning of the Chametz, often also requires self-sacrifice and dedication. It takes taking a leap of faith, following G-d into the desert and jumping into a raging sea.
Sometimes that self-sacrifice is not simply requested, it is demanded. An example of that is the commandment of the half-shekel. As Adar begins, an announcement is made for everyone to give the half-shekel and payment is made voluntarily. As Adar comes to a close, however, if someone does not give, the court comes and takes it involuntarily (like our taxes).
The half-shekel represents the fundamental concept that each of us is just a "half." Rashi teaches us that Hashem showed Moshe a "fiery" half-shekel when he explained the Mitzvah to Moshe. Our sages teach us that it was the Mitzvah of the half-shekel that saved us from extinction in the hands of Haman in the Purim story, and in the Torah itself it is stated that,
"When you take the sum of the children of Israel according to their numbers, let each one give to the Lord an atonement for his soul when they are counted; then there will be no plague among them when they are counted." (Exodus, Chapter 30:12; interestingly this is also the year of the census in the US)
May we be able to learn from the teachings of this month and merit the complete redemption, now.