You don't. I've never seen any standings for arguments won and lost, like I do with baseball or football scores in the newspaper. So I guess no one's keeping score. Unless you are. Secretly. In which case, no one of substantial importance will see your tally sheet. So why keep it?
Somewhere along the way, we became convinced that winning arguments mattered, as if the Commissioner of the Argument League was keeping track of wins, losses, and ties. I looked on Wikipedia forever. No such person or position exists.
This doesn't mean you should stop having arguments, disagreements, or - best of all - discussions. Dialogs and debates enlighten, convince, and motivate. By all means, disagree. Progress depends on it. But just know that the point isn't necessarily unity of thought.
It's okay to leave an argument having not convinced everyone. It's okay to change your mind, too. Admitting you were wrong about something means you were smart and courageous enough to decide to think differently in the name of change, improvement, and betterment. Good for you.
Have arguments that are worth having. Fight until you have no energy on the things that are important. Laugh at the things that aren't and then go have a drink. You'll be a lot happier when you realize it doesn't matter whether that car you saw last week was red or blue.