1) Does a mitzva 'enable' future mitzvot? 

Rabbeinu Yonah questions Ben Azzai's dual reasons for pursuing mitzvot and avoiding aveirot, respectively. Initially, the Mishna claims that one mitzva 'INDUCES' (goreret, which literally means to drag but functionally means to instigate or induce) further mitzvot whereas the Mishna subsequently claims that the REWARD for a mitzva is another mitzva. Essentially, the first term highlights a natural condition whereby religious behavior facilitates continued religious success. Breaking inertia and commencing religious behavior is oftentimes more difficult than sustaining such success. Once a person regulates himself to religion, his future performance will be eased. Alternatively the second concept in the Mishna- that "a mitzva's reward is another mitzva"- suggests some form of Divine assistance or enabling. In addition to natural advantage, an earlier mitzva assures Divine aid toward performance of additional mitzvot. Though Judaism does not endorse pre-determinism, and champions absolute freedom of choice at every stage of human experience, it nonetheless allows Divine support for humanely chosen lifestyles. If a person chooses to indulge in mitzva performance, Ben Azzai claims, he will merit Divine assistance in performing additional deeds. In fact the Gemara in Bava Batra (9b) provides a concrete example of this form of Divine assistance: if a person pursues the mitzva of Tzedaka, Hakadosh Baruch Hu provides even greater financial abilities to maintain his level of performance.

2) Zerizut

The Mishna actually begins by describing someone who SPRINTS toward a mitzva evoking the value of 'zerizut' in the performance of a mitzva. In fact, the conditioning effect - that one mitzva will condition toward future mitzvot may only apply to someone who enthusiastically and energetically performs a mitzva. By displaying this attitude, he demonstrates that a mitzva is an opportunity and not a burden. This mentality reflects and generates an attitude which facilitates future performance.

The Gemara in Berakhot (6b) derives the trait of zerizut from Avraham Avinu who displayed zeal in personally attending to the needs of his angelic visitors. Additionally, the Gemara in Pesachim (4a) records how Avraham arose early to embark upon the Akeida. This first portrait displays his zeal while the latter his alacrity - two traits which compose zerizut.

Alternatively, the Rambam, in his commentary to Avot, highlights Moshe Rabbeinu's behavior as a model of zerizut. Knowing that arei miklat would not become operative until the Land of Israel had been allocated, Moshe still seized a mitzva opportunity and delegated three cities in the East Bank as arei miklat. Unwilling to forfeit a mitzva opportunity, he participated in the beginning of a process which would only be completed posthumously. This portrait addresses a related but independent aspect of mitzva performance. Avraham's behavior demonstrates the RAPIDITY by which mitzvot should be performed as well as the requisite ENERGY which should be generated. Moshe's sense of urgency speaks more to a fear of a mitzva slipping out of a person's grasp. In each instance, Avraham did not harbor fear that a mitzva would expire. He rather displayed vigor and enthusiasm to perform a mitzva in a personal and passionate manner. Moshe is filled with a wistfulness about miztvot which causes him to grasp an opportunity, which, legally, may not even have been considered a mitzva since the city's operation as a refuge was delayed by many years. Yearning for even an 'unofficial' share of a mitzva, he seizes his chance.