Solely based on my most recent personal experience—being emotionally compatible. I mean HOW you handle communicating through disagreements, communicating and handling things that bother you or that you are sensitive about, and IF you are very different in those regards being willing to understand each other’s emotional needs and work with each other on them. My recent ex and I were on the same page about every single thing you can think of when it comes to compatibility- goals in life, outlook on life, kids, relationships with family, financially, had different but complementary hobbies and supported each other in pursuing them...completely fell apart due to this screaming lack of emotional compatibility. If one person is unwilling or unable to meet the other halfway in that regard, its just not going to work. Disagreements and sensitivities are going to come up no matter what. If you can’t work to resolve them together or have completely different approaches to this and don’t give each other leeway and understanding around it... it doesn’t really matter what else seems to be working.