We learn that in this week's parshah, Bo, the final three makkos were meant to demonstrate to everyone, yid and goy alike, that Ani Hashem. These plagues are then interrupted by a discussion of Rosh Chodesh, the korban pesach/Pesach observance, and redemption of the first-born. What does this order suggest?
If we contemplate for a moment that the yid in Egypt who had survived the plagues (since most of the yiddin had been wiped out during the plague of darkness) and "made it to the final cut", as it were, and were included in the exodus, one might find the need to demonstrate Hashem's ultimate rule as unnecessary. The remaining Jews had seen that no-one, even the yiddin, escaped judgement; that they found themselves alive at that late stage should have simply filled them with amazement and unequivocable, whole-bodied devotion to Hashem.And yet Hashem reasoned otherwise.
In short, a major factor in stressing Ani Hashem was for the klal's benefit. That said, the purpose of introducing the other mitvos becomes clear: in each instance, the mitzvah serves to underline that Hashem rules all, and that we are but here to serve him. It is the nature of humans to believe that we control our dalet amos to a certain degree. We plan our day, we set up and maintain our homes, we create families. While we simultaneously recognize that all of these elements are in fact Hashem's doing, our yetzer hara is always trying to convince us that we actually have more control over our lives than we do. The fact of the matter is that while we do have free choice, and Hashem hopes that we will choose good, Hashem is Master and Commander of the minutiae of our days.
Each mitzvos cited in Bo is a case where humans are prone to attribute more kavod to themselves than is due. With Rosh Chodesh, we are reminded that our concept of time, days, weeks, months and years is governed by Hashem. With the korban pesach, we are reminded that the yiddin did not have enough merit that year for the exodus, that they required the additional details of the korban pesach that first instance to earn that merit. And finally, with the redemption of the firstborn we are reminded, at the precise moment when we feel most keenly like Hashem, that first true moment ever of "Look what I created", of the fact that ultimately life is His decision alone.
In this way, these mitzvot serve as constant defenses against the yetzer hara, and keep all honour and respect where they should be, namely with Hashem.