Each Partner Needs to Accept the Other
I understand where you’re coming from on this, but my first reaction was whether our visitors would. Then I thought about why they might not get it, and decided that would be for one of two reasons: they can’t find it in themselves, or they can’t see it in their partner.
So let’s look at these two cases separately. Not finding it in themselves is addressed by your post; it’s necessary to look inside at what you want, and what is important, and not get snagged on what is unimportant.
When your partner is still working on these issues, be a rock in the stream; do not let yourself get swept up in their drama. Don’t let your anger rise in response to theirs; that only gives them more material and justification. Don’t let their accusations make you feel guilty or vengeful. Instead, just empathize with their plight. Of course, this all assumes you’ve looked inside yourself and decided their plaint is unjustified.
By so behaving, you limit the possibility of conflict escalating. After all, it takes two to tangle. As to the future, there are several possibilities. Your partner may never change. They may get bored with not having a foil for their fights. Or they may get it, and realize the folly of struggle over small things. Whatever happens, when you take the path of peace, changes for the better occur.