I'm extremely fortunate to have a partner that valued what we had enough to stick around for a long time but, this past year, it was starting to reach a breaking point. That lead to big talks, some scary but polite, some loud and angry. A lifetimes worth of under-the-surface stuff all came out over just a few months.
What I think we figured out is that we have "compatible" (co-enabling) anxieties that keep our relationship mostly functional. That feels like a drastic over-simplification but accurate, I think. All I know is it feels like the most emotionally productive year of my life and our relationship is way better now. However, I still haven't figured out how to tone down the anxiety much :)