Know When Not
Arguing for the sake of winning -- or just for the sake of arguing -- never works. Spend time figuring out what your priorities are. You don't want to fall in the trap of defending everything or defending nothing. What are you unwilling to negotiate or compromise? Make a list, or write it out in your journal.
For the sake of peace, women often give in. That's fine, except for when you put your priorities behind someone else's. You're armed with the list from the first step. When those priorities are tested, check in with your gut. Trust your instincts to defend what's most important to you.
This one's a toughie. One little word can be incredibly difficult to say, but you have to hone the ability to say no to keep your priorities straight. If your number one priority is to spend every Sunday hiking with your dogs, feel free to decline your partner's office party that would interrupt your favorite activity. Create a few good responses, like, "Thanks for asking, honey, but no thank you." Or try, "That sounds like something you would enjoy more than I would. Go ahead without me!"
If you're going to stick to your guns, you're going to get some push-back because your priorities will never be the same as someone else's. If you've determined your priorities and said "no" in the face of a priority-compromiser, you might be called unreasonable, inflexible or worse. Let it roll off your back. And if you can't, pretend that you can.
By now, you're probably feeling pretty empowered to defend your priorities. Remember, there are areas where it is better to compromise for the sake of harmony in a relationship. So if something isn't on your list of top-most-important priorities, then consider a compromise. You never know: Something less important to you might just be on your beau's priority list.