The theological truth of the Assumption is important because it is directly connected to the truth of the Immaculate Conception, which is directly connected to the truth of the Incarnation, which is, of course, the central truth of human history. So I give the assent of faith to the Assumption because I recognize the theological superstructure of which it is a part (and because I do not wish to incur that bloodcurdling anathema at the end of Munificentissimus Deus, about which more in a moment). But incorporating the Church's dogma of the Assumption into my everyday life as a Catholic is a bit harder to do.
The teaching doesn't particularly make me love the Blessed Virgin Mary more. To be honest, I find the Annunciation--and the heroic example of humble trust in God that it provides--to be a vastly more moving incident in Mary's life. Nor does the Assumption really teach me anything new about the Last Things or our eternal destiny. The Church is wisely vague about whether Mary even "died" as we understand the word, or whether being bodily assumed simply marked the end of her earthly life as death marks the end of ours. We know (hope) that someday, after we die, we will once again be both spirit and glorified body with God as Mary is now, but we would know that even if we knew nothing of the Assumption.
"Give me something I can use" is my not infrequent reaction to the more rarefied and abstract elements of Christian theology. For a long time, though I acknowledged it as true, I couldn't find much useful in the truth of the Assumption. Then, fairly recently, one passage from Munificentissimus Deus, the apostolic constitution in which Pope Pius XII defined the dogma, jumped off the page at me. Maybe it was because, after 60 years, the Pope's words still seemed so timely:
We may hope that those who meditate upon the glorious example Mary offers us may be more and more convinced of the value of a human life entirely devoted to carrying out the heavenly Father's will and to bringing good to others. Thus, while the illusory teachings of materialism and the corruption of morals that follows from these teachings threaten to extinguish the light of virtue and to ruin the lives of men by exciting discord among them, in this magnificent way all may see clearly to what a lofty goal our bodies and souls are destined.
We are not just spirits longing to be freed from inconvenient and corruptible bodies so that we can get closer to God. Our eternal destiny is as much the destiny of our bodies as it is of our souls, because our bodies belong to God too and will be saved by and in him along with the rest of what makes us who we are. Reminding ourselves of that from time to time (say, every August 15?) should make living in the body a very different undertaking for the Christian than it is for anybody else. It should help us, as Pope Pius XII suggested, to withstand "the illusory teachings of materialism and the corruption of morals that follows from these teachings." In the Collect for the Feast of the Assumption in the extraordinary form, Catholics pray that by looking always to the things of heaven ("ad superna semper intenti") as Mary did, we might be worthy to share in the same glory ("ipsius gloriae mereamur esse consortes") that now is Mary's. What she was, we are. What she is, we can become.
* * * * *Getting back to Munificentissimus Deus for a moment. It is well worth reading, among other things for Pius' thorough review of the history of the dogma, showing that it has been a tradition of the Church from ancient times--not one of those useful fictions that non-Catholics think the popes are always concocting to consolidate their own control over the rest of us. As formal dogmatic definitions have conventionally done, it concludes with an anathema, which somehow sounds especially forbidding in the original Latin:
Quamobrem, si quis, quod Deus avertat, id vel negare, vel in dubium vocare voluntarie ausus fuerit, quod a Nobis definitum est, noverit se a divina ac catholica fide prorsus defecisse.
("Therefore if anyone--God forbid--should dare of his own free will to deny or to call into question what We have defined, let him know that he has completely fallen away from the divine and catholic faith.")
I guess some people might say that that sounds pretty medieval (especially the kind of people who regard "medieval" as a derogatory term), and that we live now in an age of kinder, gentler papacies--"God's Rottweiler" notwithstanding. But to me there's something singularly healthy about a straightforward statement to the effect that "This is the Catholic faith, and the Catholic faith is serious business." To speak in that way is to treat people as adults, which is the best way of encouraging people to act as adults.