One of the reasons that this Shabbos is referred to as Shabbos HaGadol is because of the great miracle that occurred on the Shabbos prior to the Pesach of Yetzias Mitzrayim. Hashem commanded Bnei Yisrael to take sheep, the Egyptian deity, and tie them to their bedposts four days before they were to be slaughtered. The close proximity of the animal would allow them to examine it daily and ensure that it would be blemish free at the time of slaughtering. The first of the four days fell out on Shabbos. Despite the fact that the Egyptians were aware of Bnei Yisrael's intentions to slaughter their deity, they did not harm Bnei Yisrael in any way - a true miracle!
What was the purpose of putting Bnei Yisrael into such a position in the first place? Couldn't they wait until after they were freed to slaughter the sheep instead of aggravating their masters? Rashi (Shemos 12:6) cites Chazal who deal with this question. When the time came to redeem Bnei Yisrael, there was an impediment to the redemption: Bnei Yisrael were bare of mitzvos i.e. they were missing the merit necessary to attain the redemption. Therefore, Hashem gave them two mitzvos to perform: the mitzvah of korban Pesach and the mitzvah of bris milah. It was imperative that Bnei Yisrael perform these mitzvos before the redemption because their fulfillment would give them the merit they so badly needed.
Regarding Bnei Yisrael's performance of these two mitzvos, Hashem said, "And I passed you and saw you wallowing in your blood (of the korban Pesach and the bris milah) and I said to you, 'With your blood you shall live'" (Yechezkel 16:8). Ironically, the mesirus nefesh demonstrated by Bnei Yisrael did not result in the loss of life. On the contrary it produced the opposite effect; it gave them life. True life is only achieved by going the extra mile. Bnei Yisrael slaughtered the Egyptian deity without worrying about the repercussions of such an action and they circumcised themselves the day before they set out on a journey into the wilderness. They endangered their lives and Hashem repaid them by giving them life.
This concept is the essence of nisyonos - the trials with which Hashem tests a person. It is only by passing a test that one can attain the highest levels of spirituality. The Gemara relates that Dovid Hamelech asked Hashem if he could be the fourth "wheel of His chariot" in addition to the three forefathers. Hashem responded that they were tested and only by passing a test did they reach their awesome levels. When one is put to a test and, despite the difficulties, he is moser nefesh for Hashem, Hashem repays him handsomely.
Although we daven daily not to be tested with nisyonos, invariably nisyonos do arise (with great frequency). A nisoyon is not always to the degree of destroying someone else's god before his very eyes. For some getting up in the morning on time for davening is quite a test, while for others overcoming anger is a little challenge. For many, the days of bein hazmanim and Yom Tov are a true test. How do they spend their time when they are free from their normal curriculum? Every test is an opportunity to demonstrate to Hashem how far we are willing to go for Him. One should bear in mind that it is certainly worth going the extra mile, because He pays very handsomely!