Swearing can also be a great tension-release. If my wife and I aren't quite seeing eye-to-eye about something, and the pressure is beginning to rise, one of us invariably tells the other to "Go fuck yourself!" - it's our little signal that we don't want the disagreement to go any further, that we regret getting into this position, and we both fall about laughing, give each other a hug, and forget about whatever we were 'debating'.