The reverse takeaway is perhaps even more valuable. Most are not going to be as angry as you expect them to be. When you mess up don't hesitate to tell people, it's going to be okay.
1) If you try to hide the mistake I'll be mad. As soon as you know there's a problem, we can mitigate the damage by addressing it immediately.
2) I want to see that you're learning from it. A pattern of repeated mistakes may take some explaining.