You have the same choices to make about what you "feed " your mind. That movie or TV show might look good or everyone might be watching it, but the bad parts are poison to your mind. In Psalm 119:9 it asks us how a young lady (it really says man, but we know it means us, too) can stay pure. In chapter 101 it deals more about what you will put in front of your eyes (look at) or allow in your home (vs. 2-3,7). If you are trying to be a Godly girl and be pure, you must keep your mind pure. If your mind is pure, the rest of you will be, too. (I Cor. 15:33)
If you don't know if a movie is good or not, http://www.pluggedin.com/ is a good source to use. It will tell you if there are bad words (and how many), sexual content or any thing else you need to know or might wonder about.