If I have to do the returning, why ask God to bring me back?
It is a fair question. The line says "bring us back," as if God does the work. But the whole idea of repentance is that you choose to change.
The words echo Eichah (Lamentations) 5:21: "Bring us back to You, Hashem, and we will come back." The verse itself puts both parts side by side.
A Midrash on it (Eichah Rabbah, a collection of ancient teachings on Eichah) turns it into an argument. The Jewish people say: Master of the universe, bringing us back is up to You. God answers: it is up to you, as it says in the book of the prophet Malachi, "Return to Me and I will return to you." The people answer with a verse from Tehillim: "Bring us back, God of our salvation." The Midrash ends by quoting the verse with both halves: "Bring us back to You, and we will come back."
The Midrash does not say who is right. The Torah Temimah (a commentary by Rabbi Baruch Epstein, written around 1900) reads it as saying that returning needs help from both sides. God's part is "bring us back." Ours is "we will come back."
Abudarham ties the phrase "bring us back in complete repentance" to this same verse. He reads it as: if we have started to return, help us finish. He points to a saying of the Sages, found in the Gemara in Yoma: one who comes to purify himself is helped. So the order is that you start, and you are helped.
The Rambam says plainly that since every person's free will is in his own hands, a person should work to repent. On Abudarham's reading, then, the prayer does not replace the effort. It asks for help with it.
The question stays partly open. The sources agree that both sides matter. They do not give a formula for where one ends and the other begins.
Eichah 5:21,Eichah Rabbah 5:21,Torah Temimah on Eichah 5:21,Abudarham, Weekday Prayers, Amidah,Yoma 38b,Rambam, Laws of Repentance 7:1Why does understanding come before returning? And what if I would rather not understand?
The Gemara in Megillah 17b asks why the blessing about repentance comes right after the blessing about understanding. Its answer is a verse from Yeshayahu 6:10: "his heart will understand, and he will return, and be healed." The order of the blessings follows the order in the verse.
The Gemara then asks why healing is not the next blessing, since the verse says "healed" right after "return." It answers that the healing in that verse is not about sickness. It is the healing of being forgiven. Radak (Rabbi David Kimchi, a medieval Bible commentator) agrees: healing of the soul, which is forgiveness.
Here is something the Gemara does not quote. In Yeshayahu itself, this verse is not a promise. In its plain words, God tells the prophet to make the people's heart dull and their ears heavy, "lest" they understand and return. Rashi (the medieval commentator on the Bible and Talmud, from France) reads it as a description of what the people were doing to themselves. They set their hearts not to listen to the prophets, because they were afraid the words would win them over, that they would understand, and return.
So the same verse has two sides. Read Rashi's way, it describes people who avoided understanding because it might change them. The Gemara takes the chain, understand, return, be healed, and makes it the road the blessings follow.
The Tur puts the link in one line: understanding brings a person to repentance. The sources do not explain how to get from knowing to doing. They say the road starts with understanding. Rashi adds that some people hold back from it because they can see where it leads.
Megillah 17b,Yeshayahu 6:10,Rashi on Yeshayahu 6:10,Radak on Yeshayahu 6:10,Tur, Orach Chaim 115What does "complete" repentance even mean, if I keep messing up?
The line asks to be brought back in "complete" repentance. That can sound like a standard nobody meets. The Rambam (Maimonides) sets out what repentance is. A person stops the wrong thing, puts it out of his mind, regrets the past, decides in his heart not to do it again, and says it out loud.
He also names the highest level. It is when the same situation comes up again, you are able to do it again, and you walk away because of your repentance, not out of fear or weakness. His word for this is gemurah, finished. The prayer's word is shelemah.
Right away he says a lesser attempt still counts. If someone only changes in old age, it is not the best repentance, but it helps him, and he is a person who has repented. Even someone who sinned all his life and repents on the day he dies is forgiven.
He also widens what repentance covers. It is not only for big acts. A person has to look at his bad traits too: anger, hostility, jealousy, mockery, chasing money and honor. He says these are harder to leave than sins that involve an act, because a person gets sunk in them.
And a person who has repented should not think he is far from the righteous. He is beloved and desirable to God as if he had never sinned. The Rambam quotes the Sages: where people who have repented stand, even the fully righteous cannot stand.
Rambam, Laws of Repentance 2:1,Rambam, Laws of Repentance 2:2,Rambam, Laws of Repentance 7:3,Rambam, Laws of Repentance 7:4