They take work home. They stay up late working and planning for the next school day. Then, at the end of the week, they are so worn out that they don't feel like doing anything but sit around and watch television. Boooo.
Don't let your teaching job wear you down or make you lose connection with the human race.
If you have a family, get out and do something fun on the weekend. Hang out with other families. If you are single, get out and mingle. Make yourself if you have to. Don't let your life pass you by.
Teaching is a great profession, but it is a sacrifice. Just be sure you don't sacrifice everything for it.