Do you know that my first lesson ever was a complete disaster and I walked out of that class swearing I'd never go back. My teacher trainer hummed and hahed, nodded sympathetically and then shoved me back in again when I wasn't looking and here I am, 15 years later and a teacher trainer myself!
So, what I'm saying is, don't get worked up about it. It may not have gone as you thought it would but that's also to be expected. Students can't be programmed beforehand and there will always be reactions you didn't plan for.
That said, don't forget that you are the teacher and you can always pull things back on track if they veer too far off. Remember also, that you will always be learning, throughout your entire teaching career. Would it make you feel better if I said that sometimes, I walk out of a lesson feeling a bit put out because the games flopped or things didn't go as I thought they would? It happens.
So, what happened exactly that has you so discouraged?