Summa Theologica
Most of us have done something terribly wrong to another person. We realized it at the time or afterwards. For those with an intact conscience, there was overwhelming shame and a burning, seemingly inextinguishable guilt. Perhaps there was an admission, maybe to the victim, from whom forgiveness was asked. Perhaps there was only self-confession. If the shame overwhelmed and the guilt burned deeply, there may have been a redemptive pledge not to commit the same transgression and to improve a deficient character.
No one caught in throes of such a wrenching experience would characterize his emotional state as happiness. Indeed, depending on the transgression and the emotional reaction, happiness might have seemed forever out of reach.
If a tormented conscience makes one miserable, doesn’t that suggest that a clean conscience is necessary for more salutary emotions? Conscience is often thought of as an internal control system, allowing us to recognize right and wrong and helping deliver us from evil. Many religions and secular philosophies envision perfect alignment between individual conscience and the morality they embrace.