I spent years with someone with weatal health issues, diagnosed with severe anxiety but I always believed depression also even though he disputed it.
When things were good, it was amazing and a more decent man you couldn't meet.
But when things turned, they were worrying, miserable and stressful.
He didn't refuse all help but it was a case of do therapy & take medication and after a while decide they were cured. Stop both & the cycle would continue.
It got to the stage where I began to notice I was miserable, worried and always came last. There were 3 of us in the relationship him,mental health and me,with me never ever being a priority for even 5 minutes.
Guilty and sympathy also played a large role in my reason to stay. When everything was good, he would never even realise how difficult it was while he had been ill.
I finally left and it was like a weight had been lifted.
You cannot love someone better.
You cannot help someone that refuses to be helped.
Mental health is not an exercise for shitty behaviour - lots of people suffer but don't blame their partner.
It is not your job to fix it.
Your own health will suffer too.
It's an entirely different situation where someone is doing everything they can to help themselves. Following medical guides etc.