Personal pride leads to all relationship downfall. It society were to move toward empathy and understanding one with another we would be able to salvage relationships and marriages on a scale of astronomical numbers.
In my past relationships there have been a number of factors that have gone wrong, but I think the big one with the one I actually married was going ahead with the relationship even though I knew it was a bad idea. We all have that little voice in our heads, we need to listen to it.
As for me...getting ready for marriage #2, his #3, and this definitely feels like the last one ...learning to honestly communicate with each other is another big one, and being willing to shoulder an equal load to that of your partner.