Is teshuva done for each mitzvah individually?
What if you realistically feel that you don't have it in you (yet) to refrain from commiting a certain sin ever again?
Rambam, Hilchos Teshuvah 2:1-2:
אֵי זוֹ הִיא תְּשׁוּבָה גְּמוּרָה. זֶה שֶׁבָּא לְיָדוֹ דָּבָר שֶׁעָבַר בּוֹ וְאֶפְשָׁר בְּיָדוֹ לַעֲשׂוֹתוֹ וּפֵרַשׁ וְלֹא עָשָׂה מִפְּנֵי הַתְּשׁוּבָה. לֹא מִיִּרְאָה וְלֹא מִכִּשְׁלוֹן כֹּחַ. כֵּיצַד. הֲרֵי שֶׁבָּא עַל אִשָּׁה בַּעֲבֵרָה וּלְאַחַר זְמַן נִתְיַחֵד עִמָּהּ וְהוּא עוֹמֵד בְּאַהֲבָתוֹ בָּהּ וּבְכֹחַ גּוּפוֹ וּבַמְּדִינָה שֶׁעָבַר בָּהּ וּפָרַשׁ וְלֹא עָבַר זֶהוּ בַּעַל תְּשׁוּבָה גְּמוּרָה. ... וּמַה הִיא הַתְּשׁוּבָה. הוּא שֶׁיַּעֲזֹב הַחוֹטֵא חֶטְאוֹ וִיסִירוֹ מִמַּחֲשַׁבְתּוֹ וְיִגְמֹר בְּלִבּוֹ שֶׁלֹּא יַעֲשֵׂהוּ עוֹד ... וְצָרִיךְ לְהִתְוַדּוֹת בִּשְׂפָתָיו וְלוֹמַר עִנְיָנוֹת אֵלּוּ שֶׁגָּמַר בְּלִבּוֹ:
What is a complete repentance? One who has an opportunity to repeat a past sin and refrains from it because of his repentance - not because of fear or physical weakness. How so? Take one who had illicit relations with a woman, and some time later he was secluded with her. He stands in his love for her, and in his physical strength, and in the country in which he previously sinned [so he’s not humbled by being away - see 2:4] but nevertheless refrained and did not sin - that is one who does a complete repentance. ... And what is repentance? That the sinner abandons the sin, removes it from his mind, and concludes in his heart never to do it again. ... And he must admit his sins aloud and say these things he has concluded with his heart.
So, in summary, Teshuvah has four parts:
But this doesn’t really answer your question. What if one doesn’t think he stands a chance? We’re all human. We probably all fall into this category for at least one sin at at least one point in time. Those of us who aren’t big Gedolim probably more so in either of both these respects. I know I personally have remorse over certain sins, yet I can’t seem to be able to shake them. Well, most of the parts of the Rambam that I skipped are just pesukim to back up his assertions, but there was one other piece that I skipped:
וְיָעִיד עָלָיו יוֹדֵעַ תַּעֲלוּמוֹת שֶׁלֹּא יָשׁוּב לְזֶה הַחֵטְא לְעוֹלָם שֶׁנֶּאֱמַר (הושע יד ד) "וְלֹא נֹאמַר עוֹד אֱלֹהֵינוּ לְמַעֲשֵׂה יָדֵינוּ" וְגו:
[If one goes through this process,] the One Who knows all hidden things will testify about him that he will not repeat these sins ever, as it says, “And never again will we call our handiwork our god” (Hoshea 14:2).
Well, that seems an awfully odd derasha. Here’s the passuk in full:
אַשּׁ֣וּר ׀ לֹ֣א יוֹשִׁיעֵ֗נוּ עַל־סוּס֙ לֹ֣א נִרְכָּ֔ב וְלֹא־נֹ֥אמַר ע֛וֹד אֱלֹהֵ֖ינוּ לְמַעֲשֵׂ֣ה יָדֵ֑ינוּ אֲשֶׁר־בְּךָ֖ יְרֻחַ֥ם יָתֽוֹם׃
Assyria shall not save us. No more will we ride on steeds, nor ever again will we call our handiwork our god, since in You alone orphans find pity!
What is it about this verse, once put into context, that the Rambam sees as indicating that one who does Teshuvah won’t sin again?
The Kesef Mishnah says that’s exactly the problem - we haven’t added enough context. Let’s go back to verse 2:
שׁ֚וּבָה יִשְׂרָאֵ֔ל עַ֖ד יְהוָ֣ה אֱלֹהֶ֑יךָ כִּ֥י כָשַׁ֖לְתָּ בַּעֲוֺנֶֽךָ׃ קְח֤וּ עִמָּכֶם֙ דְּבָרִ֔ים וְשׁ֖וּבוּ אֶל־יְהוָ֑ה אִמְר֣וּ אֵלָ֗יו כָּל־תִּשָּׂ֤א עָוֺן֙ וְקַח־ט֔וֹב וּֽנְשַׁלְּמָ֥ה פָרִ֖ים שְׂפָתֵֽינוּ׃ אַשּׁ֣וּר ׀ לֹ֣א יוֹשִׁיעֵ֗נוּ עַל־סוּס֙ לֹ֣א נִרְכָּ֔ב וְלֹא־נֹ֥אמַר ע֛וֹד אֱלֹהֵ֖ינוּ לְמַעֲשֵׂ֣ה יָדֵ֑ינוּ אֲשֶׁר־בְּךָ֖ יְרֻחַ֥ם יָתֽוֹם׃
Return, O Israel, to Hashem your God, for you have stumbled because of your sin. Take words with you and return to Hashem. Say to Him: “Forgive all guilt and accept what is good; instead of bulls we will pay [the offering of] our lips. Assyria shall not save us. No more will we ride on steeds, nor ever again will we call our handiwork our god, since in You alone orphans find pity!”
Now we get a different picture. I quote the Kesef Mishnah in full:
ויש לומר דהכי קאמר יקח לעד להשי''ת עליו שלא ישוב לחטוא עוד שנאמר ולא נאמר עוד וכו' כלומר שתחלת הפסוק הוא קחו עמכם דברים ושובו אל ה' ומה תאמרו לא נאמר אלהינו למעשה ידינו שהיא עבודת כוכבים הרי פשטיה דקרא שלוקח לשם יתברך לעד עליו שלא ישוב עוד לאותו עון:
And there is to answer that this is what [the verse] is saying: he will take as a testimony for Hashem regarding himself that he will not sin further, as it says, “Nor ever again will we say, etc.” That is to say: The beginning of the passage is “Take words with you and return to Hashem.” And what is the meaning of “nor ever again will we call our handiwork our god”? That is a reference to idolatry, and so the simple reading of the verse is that he takes for Hashem, Blessed be He, as a testimony regarding himself that he will never again return to that sin.
I originally understood this to mean that one who sins and does a full repentance gains Divine assistance to never repeat it. But then I saw the Lechem Mishnah.
The Lechem Mishnah comes at the problem from a slightly different angle:
וא''ת איך הקב''ה יעיד עליו כך וכי לא נשארה הבחירה בידו . ... ויש לומר דפירושו כך שבשעה שהוא עושה תשובה צריך שיקבל עליו לעד להשי''ת שלא ישוב לזה החטא לעולם והוא על דרך ואעידה לי את השמים ואת הארץ שמקבל עליו לעדים לשמים ולארץ...
And if you will ask: How can G-d testify about him [that he will never again sin]? Do we not have free will? ... And there is to answer that its explanation is as follows. When one does Teshuvah, he must accept Hashem as a witness upon himself that he won’t sin again. This is similar to “and I appoint as a witness the heavens and the earth,” that he accepts upon himself the heavens and the earth as witnesses. ...
He concludes by bringing a proof to this understanding from a different passuk.
As the Kesef Mishnah uses the same wording of “accepting upon himself as a witness,” it could be that this is what he means as well: it’s not an issue of siyata d’shmaya so much as it being a fact that one who refrains from sinning because of his Teshuvah won’t sin again. If he goes through the Teshuvah process properly, he doesn’t need to worry about doing it repeatedly. All he needs is just once.
Once he truly transforms himself because of his Teshuvah, it completely leaves his mind as an option, like how one who grows up eating nothing but kosher doesn’t even consider eating treif. It’s not in his nekudas habechirah, loosely translated as his options to choose from - because he doesn’t even want to choose it at that point.
This is no easy task - not just to refrain, but to refrain because he is a new person because of his repentance. I won’t sugar-coat it for you. But it’s still much easier than many make it out to be. You don’t need to worry about your entire future: all you need to do is succeed once. And from there, one mitzvah leads to another.