"Guilt" is a self-generated sense of judgment about ourselves and our actions or thoughts, while "shame" is a reflection of judgment about us from others. Things like honor killings and ritual suicides come from societies that set right a social order by giving those "shamed" a way to restore others' opinions about them, their families, their company, or their country, however extreme it may seem.
In our culture such practices are tough to understand, just as guilt may be an odd concept elsewhere. In shame/honor cultures one actually gains social standing by getting away with an otherwise bad act. Young Spartans successfully completed their initiation into manhood by murdering a slave; the rub was they had to get away with it. Shame didn't come from committing such a cruel act but only from the "mistake" of getting caught.
I am certainly happy we live in a "guilt" culture, since the residue of this guilt is something we hold very dear: trust. In fact, the United States has the highest level of trust in the world. The thing is, guilt just sitting in your heart or your gut isn’t good for you. From time to time we need to remember we have social norms for eliminating this simultaneously healthy and corrosive trait.
I don’t think you can ever rid yourself of all guilty feelings but it's good to eliminate the ones that really eat at you. Years ago I led a class mental rehearsal in which I took cadets through an armed confrontation where they end up shooting and killing an armed assailant. I had more than a few recruits quit the academy after that, but one in particular came to me with a very disturbing revelation.
In this cadet's head, when he pictured the paramedics working on his imaginary assailant he walked up and saw that the dying man was his brother, and he hadn’t been able to sleep since. I promptly sent this military veteran to a superb police psychologist. He returned shaking his head that he had never met a shrink like that but he felt 100% better and hadn’t had any problems sleeping since his "treatment."