Something you did and can't forgive yourself for
The canon's most serious confession is a king's, for killing his father; the Buddha accepted it, said that seeing a wrong as wrong is how one grows in the noble way, and did not say the deed was undone. That is the shape of remorse in the suttas: recognized, told to someone, followed by restraint, and not lived in. Aṅgulimāla's changed life did not stop the stones. The passages here are about that shape, and about the second arrow of punishing yourself past the point where it does anyone any good. If the person you harmed is alive and the amends have not been made, a passage is not a substitute for them. If the harm was to you, the second-arrow teachings are the ones that apply.
What the suttas say
If, while checking in this way, you know: ‘This act with the body that I have done leads to hurting myself, hurting others, or hurting both. It’s unskillful, with suffering as its outcome and result.’ Then, Rāhula, you should confess, reveal, and clarify such a deed to the Teacher or a sensible spiritual companion. And having revealed it you should restrain yourself in future.
The Buddha's instruction to his own son — the full arc — check, confess, restrain.
Where this stops: For an act that did harm. It is not for guilt where nothing wrong was done, such as a carer who cannot do everything or someone afraid that wanting a child is selfish.
MN 61:11.4–11.7 · Advice to Rāhula at Ambalaṭṭhika
Sace kho tvaṁ, rāhula, paccavekkhamāno evaṁ jāneyyāsi: ‘yaṁ kho ahaṁ idaṁ kāyena kammaṁ akāsiṁ, idaṁ me kāyakammaṁ attabyābādhāyapi saṁvattati, parabyābādhāyapi saṁvattati, ubhayabyābādhāyapi saṁvattati— akusalaṁ idaṁ kāyakammaṁ dukkhudrayaṁ dukkhavipākan’ti, evarūpaṁ te, rāhula, kāyakammaṁ satthari vā viññūsu vā sabrahmacārīsu desetabbaṁ, vivaritabbaṁ, uttānīkātabbaṁ; desetvā vivaritvā uttānīkatvā āyatiṁ saṁvaraṁ āpajjitabbaṁ.
When an unlearned ordinary person experiences painful physical feelings they sorrow and wail and lament, beating their breast and falling into confusion. They experience two feelings: physical and mental. It’s like a person who is struck with an arrow, only to be struck with a second arrow. That person experiences the feeling of two arrows. In the same way, when an unlearned ordinary person experiences painful physical feelings they sorrow and wail and lament, beating their breast and falling into confusion. They experience two feelings: physical and mental.
The distinction between the pain and the reaction to the pain.
Where this stops: The sutta grants that the first arrow lands on everyone, including the awakened.
SN 36.6:1.5–1.13 · An Arrow
assutavā, bhikkhave, puthujjano dukkhāya vedanāya phuṭṭho samāno socati kilamati paridevati urattāḷiṁ kandati sammohaṁ āpajjati. So dve vedanā vedayati— kāyikañca, cetasikañca. Seyyathāpi, bhikkhave, purisaṁ sallena vijjheyya. Tamenaṁ dutiyena sallena anuvedhaṁ vijjheyya. Evañhi so, bhikkhave, puriso dvisallena vedanaṁ vedayati. Evameva kho, bhikkhave, assutavā puthujjano dukkhāya vedanāya phuṭṭho samāno socati kilamati paridevati urattāḷiṁ kandati sammohaṁ āpajjati. So dve vedanā vedayati— kāyikañca, cetasikañca.
That’s not right, it’s not good, and I feel remorseful because of it. But I can’t undo what I have done.’ Reflecting like this, they give up lying, and in future they refrain from lying.
Remorse with its proper size — felt, named, and then turned into giving up the deed.
Where this stops: The sutta goes on to say that with a heart of boundless love no limited deed remains in force; that is about the mind's release, not about consequences to others disappearing.
SN 42.8:10.3–10.4 · A Horn Blower
Yaṁ kho pana mayā musā bhaṇitaṁ yāvatakaṁ vā tāvatakaṁ vā taṁ na suṭṭhu, taṁ na sādhu. Ahañceva kho pana tappaccayā vippaṭisārī assaṁ, na metaṁ pāpaṁ kammaṁ akataṁ bhavissatī’ti. So iti paṭisaṅkhāya tañceva musāvādaṁ pajahati, āyatiñca musāvādā paṭivirato hoti.
But since you have recognized your mistake for what it is, and have dealt with it properly, I accept it. For it is growth in the training of the Noble One to recognize a mistake for what it is, deal with it properly, and commit to restraint in the future.
Ajātasattu confesses killing his father and is met not with absolution but with this — the canon's most serious case of remorse received.
Where this stops: The Buddha accepts the confession; he does not say the deed is undone, and the sutta's ending makes clear it still bears fruit.
DN 2:100.2–100.3 · The Fruits of the Ascetic Life
Yato ca kho tvaṁ, mahārāja, accayaṁ accayato disvā yathādhammaṁ paṭikarosi, taṁ te mayaṁ paṭiggaṇhāma. Vuddhihesā, mahārāja, ariyassa vinaye, yo accayaṁ accayato disvā yathādhammaṁ paṭikaroti, āyatiṁ saṁvaraṁ āpajjatīti.
They recognize when they’ve made a mistake. When they recognize it they deal with it properly. And when someone else confesses a mistake to them, they accept it properly.
Three marks of a fool and an astute person — including how to receive someone else's confession.
AN 3.4:2.3 · Mistakes
Accayaṁ accayato passati, accayaṁ accayato disvā yathādhammaṁ paṭikaroti, parassa kho pana accayaṁ desentassa yathādhammaṁ paṭiggaṇhāti.