I've learned something in the last couple of years about arguments.
I like being right. Experience has shown me, however, that I tend to learn more when I'm open to the possibility that I'm not right.
Because of this, I've redefined what "winning an argument" means to me. It's not when I've managed to bully or cajole someone into accepting my point of view. Instead a "won argument" (or discussion) for me is one where I walk away with a knowledge or perspective that I didn't have before.
Interestingly, this kind of "winning" can be enthusiastically pursued without risking someone's friendship. In fact, some of my very best friends are ones who disagree with me in regard to opinions that I hold dearly. As I've pursued this strategy, I've gained friends and increased the nuance of my perspective. I've gained these things without losing an ounce of my own sense of self.
I've lost nothing, and have won a great deal.