For all its stewing, regret ironically does not truly focus on the past. Often it is more concerned with the present and the future and how they would be if only we had done something differently.
We try believing in more abstract concepts: justice, happiness, and self-improvement, only to find that we can never truly grasp which standards should be accepted and which should be rejected.
When guilt becomes our totem, it dictates our idea of right and wrong and enslaves us to the fear of what happens when we open our eyes tomorrow morning.
We are called to proclaim the life, death, and resurrection of the Answer incarnate, Jesus Christ, and in love respond to the questions that inevitably arise against it.