"You shall guard the matzos" (Shemos 12:17). Do not read "the matzos" but rather "the mitzvos". Just as we do not allow the matzos to become chametz [by tarrying so that the dough rises], so too we do not tarry in performing mitzvos. Rather, if [the mitzva] comes to your hand, do it immediately (Rashi).
This analogy is problematic. If one tarries and the dough becomes chametz it is not matza at all, while if one tarries in performing a mitzva, it is still a mitzva, albeit one that is missing the extra dimension of alacrity.
Rav Hutner (Pachad Yitzchak, Pesach, 1) answers this question based on the Maharal's explanation of Rashi. By delaying the time of the mitzva, one views the mitzva as being under the influence of time. Time is a part of the creation, but the refined soul of a Jew, which is heavenly, cannot be satiated by all the delicacies of this world (Koheles Raba 6:7). Therefore, the soul is above time, which was created as part of this world.
Alacrity represents the attempt to minimize the time gap between the opportunity to perform a mitzva and its completion. We left Egypt in a hurry, since this was the creation of Am Yisrael (Maharal, Gevuros Hashem chapter 51) as an entity above time. We are above time not only as an eternal nation, but also as a nation that attempts to break the barrier of time via alacrity in the performance of mitzvos. Failure to do so is not merely foregoing an extra enhancement of the mitzvah, rather it reduces the mitzva to something under the influence of time instead of being, as it should, above time. As such, it can be compared to tarrying when preparing the dough and allowing it to become chametz, which is an entirely different entity than matza.
Remarkably, the very hurriedness which was necessitated by our creation as a nation above time led to the fact that the dough we took out of Mitztrayim was matza and not chametz (Shemos 12:34). Moreover, the conclusion of the pasuk which demands alacrity (12:17) alludes to the eternity of our nation as being above time, "You shall guard this day for your generations as an eternal law."
Eternity, in practice, demands that the transcendent importance of mitzvos be taught to the next generation. Pesach is the time of, "You shall tell your son" (Shemos 13:8). Words do not suffice for this. A child must absorb his parents' attitude that mitzvos are the most important actions of a Jew. Alacrity is required to demonstrate this idea. Failure to be quick and focused in performing mitzvos risks a child's indifference to, and even abandonment of, Hashem's commands, thus endangering the eternity of mitzvos in one's family.
At a siyum we say "We run to the words of Torah, and they run to meaningless things." The Pachad Yitzchak contrasts the alacrity of the non-Torah world with the Jew's requirement to attempt to break the barrier of time by hastening to perform mitzvos.
Our children keenly observe our pace in approaching Torah and mitzvos, as well as our pace in dealing with worldly matters. In the world around us, people run to work, a necessary enterprise, but even more so to enjoyable sports and entertainment events. If we do so, and do not run to Torah and mitzvos, it conveys an attitude which can have negative impact on ourselves, and certainly on our children.
The difference between chametz and matza is exceedingly small, k'chut hasa'ara (Chasam Sofer Drush 35 for Shabbos Hagadol). On Shabbos Parshas Hachodesh, as we prepare for Pesach, our alacrity and our attitude to the mitzvos we perform can make all the difference, both for ourselves as we run to the life of the next world and for the eternity of our generations.