A problem I've noticed with current math teacher.?

Hey guys, I was reading an email from my math teacher( I'm in college) about some problems on my homework I needed help with and figured out a **** up she does all the time which pisses me off and I need help in how to deal with it cause it's making me not want to do things right on MY end. The problem is SHE gets her information wrong then has the nerve to criticize me and the rest of the class on how WE'RE doing stuff wrong. How can I not take this personally and have it affect my schoolwork?. If anybody could answer this for me, I'd greatly appreciate it, thanks and have a great day!