I wrote earlier about the need for Aaron to confront the mistake of the golden calf. The first sacrifice he is required to make after assuming the role of High Priest is a sin offering of a calf - which can only remind him and everyone watching of the episode of the golden calf. He has to confront his very public error and do teshuvah - that is, he has to answer for his mistake.
One way of being stuck and destroyed by a past mistake is by refusing to confront it, just wanting to "move on" before you have changed yourself in the way that is necessary - that is, before you have earned the right to forgiveness. We all know people who just constantly repeat awful behavior, who continue to hurt others people because they refuse to confront what they have done and take responsibility.
There is another way to be stuck - by dwelling on past mistakes and not permitting yourself to move past them. Another version of this (I think) is failure to believe that you can become something you are not, the refusal to accept that you can change and become better.
This is Aaron's problem. Several commentators write that he was too afraid to approach the altar to begin his role as High Priest (it doesn't look like this in the Torah; but the idea is based on the fact that Moses commands Aaron "Approach the altar!" and the rabbis wonder why Aaron had to be told to do so....they conclude he must have been hesitating for some reason). In a midrash we read
Aaron was ashamed and afraid to approach [the altar]. Moses said to him, "Why are you ashamed? It was for this that you were chosen." - Sifra 1:4This imagined conversation hints at Aaron's awareness of his past failures, as though he is saying to himself 'I can't possibly do this - look what a lousy person I am.....I'm really supposed to be in charge of the sacrifices? Have people forgotten who I am?"
Ramban gives an interpretation with imagery straight out of a Spinal Tap (or Ozzy) concert. He imagines that when Moses saw Aaron hesitating, he said to him....
"Have courage! Come and do your service!" For there are those who say that when Aaron looked at the altar he saw the image of an ox. Because Aaron was afraid so Moses approached him and said "My brother do not be afraid of whatever you are afraid of. Be brave and approach [the altar]"....because Aaron had the sin of the golden calf upon his soul and this sin was fixed in his mind....so it looked to him like the image of the calf, so he held back from his atonement. Therefore Moses said to him "Be bold, because God wants you to do this!" - Ramban on Leviticus 9:2-3In both of these reimaginings of the situation, Aaron is paralyzed by his memory of what he had done. His brother Moses pushes him through this guilt and hesitation. I favor the second one because it involves Aaron hallucinating a terrifying horned animal, but the basic point is the same. The first part of moving beyond past errors is doing the work to correct ourselves, to become different internally so we understand our error.
But the second, crucial part, is not becoming stuck in the self-abuse and guilt. We have to have the confidence and courage ("Be Brave!") to accept that we are not owned by our past and we can once again be "pure."
So, be brave!