A good partnership is not so much one between two healthy people (there aren’t many of these on the planet), it’s one between two demented people who have had the skill or luck to find a non-threatening conscious accommodation between their relative insanities.
The very idea that we might not be too difficult as people should set off alarm bells in any prospective partner.
We can say straight off that they occur with appalling ease and regularity.
Academic achievement and career success seem to provide no vaccines.
It can take years and situations we have had no experience of.