Terri Orbuch, author of 5 Simple Steps to Take Your Marriage From Good to Great, on how to have healthy disagreements in USA Weekend magazine:

Start with "I." Say things like, "I become anxious when you leave the stove on."

This is an important lesson. See, when you accuse people of things, they become defensive. If you say, "You have to stop guzzling Jägermeister and aiming the car at old ladies in crosswalks!" they'll say, "Hey, why don't you try and make me?" Rather than solving problems, it escalates them into fistfights.

Besides, can you ever really be sure that the other party stands alone in guilt? Frequently there are gray areas. If you say, "Stop dangling our baby out the hotel window," they might just snap back with something like, "Oh, yeah -- like you never dangled the baby out a hotel window!" Resolving the problem is forgotten in favor of a dispute about who did what.

So, when you encounter questionable behavior, take pains not to be accusatory. Don't point a finger with the word "you." Say instead, "I become anxious when your crack pipe sends flames racing up the curtains and all my belongings start to melt." With the pressure off, your partner will respond with something like, "Well, let's take you to the doctor and get tranquilizers," and then everybody goes to bed happy.