"HONOR YOUR FATHER and your mother," says the Fifth Commandment (Exodus 20:12). Honor them for having taken care of you before you were old enough to take care of yourself. Honor them for the sacrifices they made on your behalf, including the ones you would have kept them from making if you'd had the chance. Honor them for having loved you.
But how do you honor them when, well-intentioned as they may have been, they made terrible mistakes with you that have shadowed your life ever since? How do you honor them when, far from loving you or taking care of you, they literally or otherwise abandoned you?
The answer seems to be that you are to honor them even so. Honor them for the pain that made them what they were and kept them from being what they might otherwise have become. Honor them because there were times when, even at their worst, they were doing the best they knew how to do. Honor them for the roles they were appointed to play—father and mother—because even when they played them abominably or didn't play them at all, the roles themselves are holy. Honor them because, however unthinkingly or irresponsibly, they gave you your life.