End every argument like you might not see them tomorrow. Nobody gets a guarantee.

Arguments feel like they sit inside a long series, with plenty of chances to repair them later. That assumption is usually correct and occasionally is not, and there is no way to know in advance which one you are in. Leaving something unfinished costs nothing only when there is more time, which is the one thing nobody is promised.

You do not have to resolve everything before you part. Just refuse to let the last thing said be the cruellest thing available. A short line that keeps the door open is enough; the rest can wait until you are both calmer.