The Christian life is so much more than avoiding negative things. It is primarily about engaging in thoughts and activities that bring honor to God. Paul says your authority is to build up, to encourage your children. Here are two practical examples of doing this: Two young children are fussing and complaining.
"Why can't you two just be quiet! Being noisy and fussy is a distraction to everybody in this house. I don't want to hear any more unpleasantness, and I mean it! Do you understand?!?"
"God's Word says that we should be thankful for each other. Sarah, Ethan, remember that we talked about things we can be thankful for about each other? Well, this is a good time to remember those things. How does God want you to respond when your brother or sister is not pleasant?"
"That's right, he wants you to return good for evil. Excellent! Let's pray and then I can spend a little bit of time playing with you two."
A middle-school child has a difficult schoolwork assignment.
"You are still behind on this assignment aren’t you? If you had just listened to what I told you last week, you wouldn't be behind now, would you? What did I tell you? Remember, God says you must be diligent. Well, I hope you learn from this, young man. If you don't solve this problem now it will plague you for the rest of your life. This time, stay with it."