How do you discern which aspects of personal change are fundamental to your journey and therefore non-negotiable, versus those which are flexible and can be adapted to maintain a relationship?

This is perhaps a little mystical or spiritual or something, but it's kind of an intuition developed over years of reflection on who I am and what I'm becoming and what I want to become. It's previous relationships that didn't work out, and recognizing the things in those relationships that made me feel like less my self, less alive. Thinking deeply about different issues that arise in a relationship, and what my response to that issue is, and why am I responding in the way I am. What is my response telling me about who I am and what I want? What is my response trying to tell me about what my non-negotiable might be, or maybe my response is coming from a place of fear or anger from a previous relationship, and this issue isn't really a non-negotiable, it's just that my past self was wounded, and I'm subconsciously remembering that and responding based on a need to feel safe and secure. So, I meditate on these things... a lot. When something comes up that makes me uncomfortable, I slow down to ponder why that is, where is it coming from, is it a past experience or is it someone else's values I adopted that I don't actually believe but I adopted it because I wanted to once belong to a group. Maybe it's a soft 'truth' and can I be flexible with it? I future project about what could my life look like if I allowed certain things in, who would I be, and could I be happy with me if I let this thing in. For me, my non-negotiables are few, but they tend to gravitate around the idea of if I mentally play out the consequences of allowing certain things from a relationship, could I still be proud of myself? Would I still be happy with myself? Or would I live with regret? In short, my discernment comes from a place in which I try to know who I am and the forces that shaped me, and also to look at who I want to be, and make decisions that move me closer to who I want to be, knowing all the time that who I want to be is constantly changing as who I am changes.