If your character makes the same mistake again and again, it may begin to feel like they aren’t growing or developing in anyway. While that’s true, it’s not always a bad thing. If your character doesn’t change, often in a great story, the world around the character changes and that’s what makes the repeat incident more interesting the next time it comes up.
Characters who cry wolf
So let’s look at one classic example: the boy who cried wolf. We all know this one. A bored little shepherd boy watches sheep and calls out, “Wolf! Wolf!” as a joke. The town comes to his aid, but, what do you know, there’s no wolf. The boy gets scolded. But that doesn’t stop him from doing it again. When I heard this story when I was young, the boy called “Wolf” at least two more times as a bad prank. But then, we know the ending. The boy calls “Wolf!” and the town does not come to help him and there really is a wolf who gobbles him up along with his sheep.
The boy in this story does not change at all, yet that’s not really a problem here. There is still a change or new development in the way the town reacts to him. It’s not an issue that the boy does the same thing over and over again, because the consequences of his actions are different. He might not have realized that would happen, but that doesn’t matter, his situation is changed as a result of his repeated actions.
So, if your character makes the same mistake more than once, the outcome of his decision should be different the next time around. His inability to change, despite wanting to, should have consequences. This will help to keep the plot from stagnating. There are definitely modern examples where characters decide not to change their behavior and succumb to some kind of consequence, but I can’t think of any at the moment off the top of my head.