Further to my last, I have been considering the Prayer over the Gifts, particularly ". . .ut hæc sacrosancta mysteria, gratiæ tuæ operante virtute, et præsentis vitæ nos conversatione sanctificent, et ad guadia sempiterna perducant...."
I was struck by your translation of convesatione as 'conversion' [more usually conversio in Latin?].
The redoubtable Lewis & Shiort gives 'frequent use' as the primary meaning of conversatio.
Therefore, I am inclined to translate:
". . . that these most holy Mysteries, by the powerful working of your Grace, may both sanctify us in the present life by frequent use, and may lead to joys everlasting..."
Or perhaps more elegantly:
"... that these most holy Mysteries, by the powerful working of your Grace, may both sanctify us in this life by frequent use, and may lead us to joys everlasting...".
This brings out the link between this prayer and the Collect, the using of "good things of this passing life" being amplified and explained in the Prayer over the Gifts as the "most holy Mysteries" which need "frequent use", not merely limited to this particular offering of the Holy Sacrifice.
I must own up to not being a Latin scholar, my knowledge being rudimentary, so i may be barking up the wrong tree, and would be grateful for your comments.
John brings up a good point about a difficult word in Latin. This same word has had a great deal written about it in relation to what it means the monastic vows in which Benedictine's promise "de stabilitate sua et conversatione morum suorum et oboedientia."
The first and the last are pretty straightforward as "his [the monk's] stability" (to live in that monastery) and "obedience." The second one is difficult. I've seen it translated as "conversion of morals" and also as "fidelity to the monastic life."
The best understanding is that the "conversatione morum suorum" means the monk will live his life faithfully according to the monastic life, which includes virtues, obedience, chastity, poverty, etc.
(On a side note: One caveat about Lewis & Short is that it will sometimes have more of a classical Latin take and so some more ecclisastical Latin nuances may not be covered in it. That's not necessarily true in this case, but just a general note of warning when using Lewis & Short.)
As John noted, Lewis & Short shows the meanings for "conversatio" as "frequent use," "frequent abode in a place," and "conversation."
My "Dictionary of Ecclesiastical Latin" by Leo F. Stelten has "conversatio" meaning: conversation; conduct, manner of living."
Ultimately, I would say my preferred translation of "præséntis vitæ conversatióne" in the prayer over the gifts is the "way of living of the present life." I think I picked the word "conversion" in my translation because that implies a bit more virtuous living of our lives which will lead to our sanctification by God's grace through these Mysteries (which includes frequently participating in these Mysteries). However, I can see John's point too, in that frequenting these Mysteries in our lives will lead us to holiness. Although I have seen in other prayers the word "frequentatio" for the "frequenting" of things in this sense. "Et præséntis vitæ nos conversatióne sanctíficent," is just a difficult phrase to translate.
I think this is a good example where it is difficult to translate a word with so much meaning without doing tons of linguistic gymnastics.