Other researchers say forgiveness can be taught -- and can produce measurable results. Psychologist Fred Luskin of the Stanford Forgiveness Projects at Stanford University heads a series of studies of people, some with "unresolved hurts" from the likes of parents, spouses or bosses and some with very dramatic psychological injuries.

Many marriage therapists believe forgiveness between couples is mandatory. Some research suggests that when partners don't forgive each other for past hurts, they are less apt to manage conflict in the present. Luskin says adults who cannot forgive their parents for mistakes may unwittingly transfer their anger to spouses.

Dissenters say the benefits of and need for forgiveness are being oversold. "We see forgiveness as some kind of a Holy Grail," says psychotherapist Jeanne Safer, author of Forgiving & Not Forgiving: Why Sometimes It's Better Not To Forgive. "The idea is just embedded in our culture. What does that do to people who cannot forgive? They think 'I'm a monster if I can't do it, and it will be bad for my blood pressure and I'll give myself cancer.' "