It is a vicious cycle we find in life where when a person is hurt in some way by another, they either turn it into something great or something grim. It varies from person to person. For the ones that have most known pain, it can be their breaking point. A breaking point which fills them with so much sorrow and resentment that the only direction they can think in is cynical. This resentment reflects through their grieving experience that in turn is inflicted on a different human being; coming full circle, marking them for a similar grief, heightened only by freshly augmented personal struggles.
What it means for the general human experience is that it is only broken people breaking people.