if you have a relationship with someone who makes you unhappy or makes your mental health decline, then you need to leave that relationship and make yourself happy. you can't stick around and stay with someone who makes everything worse. you're not obligated to be someone's counsellor and maintain a negative relationship. you're not obligated to suffer through a relationship with someone who emotionally drains you. you have EVERY RIGHT TO LEAVE if it means you will be happier and healthier.
let me just tell you guys that if you cut negativity and people who make you sad from your life, you can be a whole lot happier. i cut someone who made my mental health worse and i've been so much happier. so please do what's best for you, because your mental health and happiness comes first.