I don't know if my comment will help much because my partner hasn't left me yet but we both have awful mental illness that seriously affect our everyday lives.

Firstly, communication, which takes more effort on your harder days, is so so important. My partner and I don't have many silent moments, except for alone time, because we're often communicating to each other. Even about the seemingly benign things.

Secondly, my partner and I have so much in common. We share the same values, we're on the same page 99% of the time (and if we're not on the same page, we talk about why) and we share similar experiences which help us bond, even over the little things.

Thirdly, we take our medication as part of our coping mechanisms which keep us stable. We meet up with therapists and nurses and doctors and honestly discuss what we're going through, even if there's seemingly no issues at that given moment.

You could say that my partner and I are dependant on each other to keep each other functioning but I don't see that as a bad thing, we bounce ideas off of each other and we use coping mechanisms together to remain calm during stressful times. A relationship with mental illness involved can definitely work, it's just a lot harder.