When you've been with someone for a long time and really get to know them, it's easy to know how to push their buttons and get an argument going. But just because you're angry about something doesn't mean you should bring it up - or just start going off on your partner about it. When you know your partner is sensitive about a particular topic, then it's unfair to form your attack around that topic. Before broaching a topic that you know is going to cause some strong feelings, take a step back. Figure out why you're mad first. Give yourself a "time out" to sort out your feelings. Take a bath, watch a sitcom, surf the Internet - anything that'll let you cool down for a few minutes. Revisit the topic, then if you still feel angry, ask yourself what's triggered your anger. Are you angry for him coming home late every day because you suspect infidelity? Or are you just missing him? Perhaps he's not pulling his weight around the house. Regardless, get to the bottom of your feelings before unloading them on him.
When it is time to confront him, there are a few things to avoid saying. On the top of that list is making accusatory statements. "You never..." "You're such a..." "How could you..." And using absolute terms, like "never" and "always" are always hot-button ways to start an epic fight. Focus on specific examples of behavior you dislike - no one does something "always" or "never." Begin with a positive statement, like, "I appreciate how you've been working so hard." Then launch into your problem: "But I'm concerned about you staying at the office so late." Remain calm, and don't be disagreeable just to cause conflict. If you can find a point that he makes that you agree with, say so.
