There are curiosities in this prayer, even controversial things, so to speak.
Converte nos, Deus, salutaris noster,
et, ut nobis opus quadragesimale proficiat,
mentes nostras caelestibus instrue disciplinis.
Today’s prayer comes from the Gelasian Sacramentary in the section for prayers from the 10th month, a time when there was a fast (think of the penitential character of Advent), but it was slightly different, saying ut nobis ieiunium proficiat. Ieiunium means "fast".
Redactors made changes to the prayer along the way. It was in the preconciliar Missal in the 1962 edition as ut nobis ieiunium quadragesimale. You can see what happened here. There was a conscious effort to reduce explicit reference to ieiunium, fast, and focus instead on opus. Opus is, of course, a work or a labor. It also has a military overtone as "a military work, either a defensive work, fortification, or a work of besiegers, a siege-engine, machine, etc." So, it is either offensive or defensive.
Disciplina is a techincal term, refering to "instruction, tuition, teaching in the widest sense of the word" which is sometimes used synonymously for ars and scientia. Scientia is the way to go here. EVen in Italian the word "disciplina" means the teaching of basic catechism. Converto is "to turn or whirl round, to wheel about, to cause to turn, to turn back, reverse; and with the designation of the terminus in quem, to turn or direct somewhere, to direct to or towards, to move or turn to". Instruo, which leads to forms such as instructus, means "to build in or into; to build,, erect, construct" and logically comes to mean also, "to set in order, draw up in battle array" and "to prepare, make ready, furnish, provide, to equip, fit out". You can see how instruo signifies "to provide with information, to teach, instruct".
In ecclesiastical use, opus is more specialized as "a work of superhuman power, a miracle" (cf. Vulgate John 5:36; 7:21; 14:10).
Convert us, O God, our salvation,
and instruct our minds by means of heavenly teaching
so that the forty day operation may be advantageous for us.
I wanted to get a touch of the military unerlayer, and so I used "operation" for opus.
Two things stand out in my mind. First, there is a military underlayer to this prayer. We have seen this in our lenten prayers before. The people listening to this is the early Church in Rome would have automatically received this layer of meaning. Second, there is a touch of Neoplatonic theory of exit and return. The idea is this, things go forth from their source, turn about in a conversion, and return to their source. This is applicable to the eternal Word and the Father and also to the soul of man which in its search for wisdom, passes through scientia (knowledge) towards sapientia (wisdom). The vocabulary of the prayer strongly suggests this Neoplatonic paradigm. The instruction of God turns us about and brings us to our proper place.
Christ Himself is the one who disciplines us in this time of Lent. He teaches us by the example of His words and deeds which we learn from the pages of Holy Scripture. He teaches us by means of the Church which gives us the holy season of Lent. He instructs us by interior movements of the mind and heart under the operation of grace, especially in regard to our consciences which may need a basic kind of conversion. We must discipline our bodies through fasting and other motifications. We must discipline our minds through proper instruction and reflection on things that are true, particularly in the One who is the Truth.