It happens so fast. You're conducting your class, then all of a sudden a student crosses the line, and you're seething. Or hurt and offended. Or caught off guard and just don't know what to do. But whatever you do, I'm going to recommend you avoid showing it because this is:
Mistake #6 - Getting Upset
I'm not going to tell you I don't get mad, hurt, offended, or intimidated in the classroom. I do. But when I feel it coming on, I do my dead-level best NOT to let those emotions get elevated, and if/when they do get elevated, I don't let it show. I might, at the most, raise my voice and tell a student to "please stop doing that." But after I address the behavior, I go back to my normal tone and keep smiling and teaching the class like nothing happened. As if nothing really fazes me.
Why? Because the generation of students we're teaching right now has a strange reaction to displays of anger, frustration, or hurt. They won't feel guilty that they made you mad or pushed you to the end of your rope. They won't settle down or change to make you feel better. If you show real anger and frustration, they'll just look at you like you're crazy. They'll possibly laugh, and will often try to make you even madder, because they think it's funny and fun. And then guess what. Your emotions get even farther out of control, and it's an endless cycle.
When I'd get to the absolute end of my rope in a class, I used to do things like just say, "Fine. I'm done teaching today. You guys do whatever you want," and go sit at my desk and pretend to work. (Not very often, but I have done it a few times over the past 15 years.) Fifteen years ago, if I did that, the class was deathly silent, not sure what to do until I decided to stand up and teach again. The last time I did that (in 2009) they just laughed it off, started talking and playing on their phones, and enjoyed the fact that they "won" the game of trying to get me not to teach a lesson so they could have free goof-off time.
I also had been known to give a class a "serious talk" the next day and let them know how frustrated and upset I was with their shenanigans in the last class, and basically plead for a change in behavior, etc. Again, that tactic did work for me 15 years ago, but now I'd be wasting my breath. Now, instead, I put all my energy into making sure they never see me sweat. They don't see me getting upset, feeling frustrated, hurt, angry, or unsure. I address the behavior and I just keep right on going with my lesson as if it's no big deal.
Over time, you really do get more accustomed to all the crazy, silly, obnoxious things that students do in class. You've practically seen it all, and it really doesn't faze you as much. But if you're a newer teacher, you want to get to that point now at least in your outer appearance. Fake it 'til you make it. Use your teacher voice, tell them to settle down so you can teach them some Spanish, and march right on with your lesson. Don't be or act surprised by the audacity of their behavior. Act like you've seen it all before. Say the names of individual kids and tell them specifically to stop talking, stay in their seat, stop picking on so-in-so, or whatever, until you can teach your lesson. Be relentless in getting that lesson taught. Have a "We've got work to do and we're doing it!" attitude, positive, firm, fun, and unruffled by their silliness.
That's my advice!