I can't stop agonizing over what I said? Cheerleading?

At cheerleading practice we were rolling up the mats, something kind of hard to do without the help of most of our squad. There were only about five of us doing it, and the rest were just kind of there, pretending to help clear up the pom poms. So, I said, "Guys, if you can help roll up the mats, please do!" in kind of an annoyed way I regretted... one of the girls comes over and says to another, "I'll only help if I don't get yelled at, because that's what happened last time." now I feel bad and I cant stop agonizing over what I said. This was yesterday, after a particularly grueling practice- everyone was tired. I really want to be captain next year... any advice on how to stop agonizing over this, as well as how to become captain?