“I have a priest friend who is preparing a former soldier for reception into the Church, he served in both Iraq and Afghanistan, he saw and did things that deeply wounded him and bears the scars of guilt. We spoke about how to deal with his guilt. Like many ex-soldiers, I suspect he has tried drink, drugs or even psychotherapy, most priests, myself included, might give a penance of a few Rosaries but really rely on allowing him to talk, in my experience this rarely works. Pre-Trent, and possibly in Orthodoxy he would have given a penance that involved a prayer of exorcism of some sort followed by some kind of real penance, public humiliation, an arduous pilgrimage or time in monastery, vigils or fasting. Outward actions, signs and symbols bring about an inward change in our attitudes, our minds and hearts often follow our bodies.

I remember being told of the Compostella Camino after the WWII being revived by former soldiers, sometimes sometimes barefoot, sometimes carrying rucksacks filled with rocks doing penance for wartime sins.”

http://marymagdalen.blogspot.com/2014/06/actions-signs-and-symbols.html