When is it time to say goodbye?

For years, I have been trying to make a certain relationship work
One that has filled my soul and spirit to the brim, but has also brought me such heartache and toxicity that has become dangerous for my wellbeing. It's no secret that I have struggled with suicidal tendencies in the past. So when a relationship can bring me to that point- to wanting to kill myself at the thought of the relationship being over - is that when it's time to say goodbye?
But what about the incredible times? What about the beautiful moments of healing and complete intimacy. Unconditional love. Then again, if it was unconditional love, it wouldn't be emotionally abusive. The other person wouldn't just shut me out when it's convenient for them. They would want to stay, to grow, to love, to talk. Maybe that's when it's time to let go... when the other person decides I am no longer worthy of their love. Their friendship. Their compassion.
The problem is, I still love this person more than words can express, the emptiness I feel without them-- it's like I can't catch my breath. The greatest panic attack meets the all consuming grief. I love her more than I've even loved past partners. (This isn't a romantic relationship, it's a soul's kinship)... We have this pull to one another I've never felt before... a magnetic energy. Yet it's interrupted by toxicity. I just want the toxicity to end, I want to begin again, I want to go back to my friend...