I think it's toughest during the first two years. I'm able to keep a pretty good balance between work and down time, but I do take my work home with me. After a couple of years, you will have a lot of reusable lesson plans in your repertoire and will spend less time planning. You will be able to make adaptations to your existing lessons instead of writing completely new ones. You can also choose not to take any work home. You can come in early and stay late as needed to finish your work. There are days when I work eight or nine hours instead of six, and I finish my work at school. Every job has its pros and cons. You need to figure out what works best for you. I would try teaching for at least two or three years. That way you can be sure that it's not the right fit for you.