As you may know yourself, you hate compromise and he is flexible. Probably you kept on explaining what you thought straight away. And normally he listened and suggested some. But probably you tried to stay with your way of thinking.
When both relationship was very good, any gap of opinion would not affect relationship. But one day cold wind blew between 2 people, gap of opinion could be serious matter for separation.
You do not need remember him. But please consider anything you might said to him too much or too straight.
Before look into yourself if anything you should not do/say. Then you will find some answer for your future happiness. Again, as I am not him or yourself, the above is just my thoughts without any ground.
If it is too much, please forgive me.