The Rational Male - Rollo Tomassi. I know it likely going to be a hated example, but nonetheless I strongly suggest to read it if you are confused or unsure about certain aspects of relationships.
As someone who has occasionally stumbled across the community around this book at Reddit, I do wonder why so many of these men keep trying. When I reached, from relationship experience, my own conclusion that any partner in a relationship would inevitably have different and incompatible goals, motivations, and outlook from own, I simply chose to live alone from then on.
Obviously people might crave companionship. But if one is frustrated in obtaining that to the point of seizing on literature like Tomassi’s book, why keep hitting one’s head against that wall?