If parents think that their child's behavior should always be excused, that child will never experience the feeling of being grateful for their successes. Children need to distinguish between the outcome of making mistakes, and the ultimate growth and strength they draw from correcting them. Then they can be grateful that they are going down the right paths.
You have to be consistent in how you present yourself -- to the point where you don't mind being "guilty of repeating yourself." If you abandon the consistency, people will get confused and the perception you are trying to change will get muddied by conflicting evidence that you are just the same as you were.