This tool is something Jordan Peterson suggests in his book 12 Rules for Life (Pillar tool 3.12). After arguing with someone, split up and go to different rooms, each intending to think of at least one small thing you could have done differently in the events leading up to the fight, or can do better in the future. Each of you should focus on changing your own actions: what you personally could have done differently. Be as honest as possible with yourself and try to expand your thinking, rather than getting stuck in your usual patterns.
This process can take just a minute or two, or considerably longer. You may find several aspects of your behavior you wish to change, or just one small thing, like “I wish I had paused for three seconds before replying to you.” However long this process takes, when both of you have determined something you want to change, meet up again and share what you came up with. At times it may be difficult to find something you want to change, but if you look hard enough, there’s always something.
The point of this tool is not to try and change the other person, or prove that you’re right, but rather to investigate what you could do better, learn from it, and improve. If you can forego blame after an argument, and instead take the opportunity to grow both as individuals and together, you may discover ways in which you truly want to change. This can be a very powerful way of sharing a journey with your partner and strengthening the relationship.