The Reason for My Fears About Behavior...

I feel like the reason I'm so worried about how my discipline plan will be in my classroom is because I've already had a bad experience working at one of the schools in Temple being a "tutor." I was working with the pre-school students and I felt like no matter what I did to discipline them, nothing ever worked. They continued to do the same thing over and over again. One girl I worked with was very stern with them and they listened to her for the most part, but every day I left mentally exhausted because I was always trying to think of something else that would get to the students and make them stop. As a result, I don't feel like I'm prepared or knowledgeable enough to know how to manage my students in my OWN classroom effectively. I know classroom management is a very important thing because if you do not have control of your students within the first week of school and have a consistent routine every day, then they feel free to do whatever they want and they are in control and not you, the teacher. Does anyone share this same fear with me? Has anyone had a similar experience, and can share some advice with me?