The Philosopher’s Mail offers some wisdom here:

All of us are crazy in very particular ways. We’re distinctively neurotic, unbalanced and immature, but don’t know quite the details because no one ever encourages us too hard to find them out. An urgent, primary task of any lover is therefore to get a handle on the specific ways in which they are mad. They have to get up to speed on their individual neuroses. They have to grasp where these have come from, what they make them do – and most importantly, what sort of people either provoke or assuage them. 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. The question is just where the problems will lie: perhaps we have a latent tendency to get furious when someone disagrees with us, or we can only relax when we are working, or we’re a bit tricky around intimacy after sex, or we’ve never been so good at explaining what’s going on when we’re worried. It’s these sort of issues that – over decades – create catastrophes and that we therefore need to know about way ahead of time, in order to look out for people who are optimally designed to withstand them. A standard question on any early dinner date should be quite simply: ‘And how are you mad?’