By all means try to understand.. But if your trying to label one specific thing as the "fault" then you will fail to understand every time, since that isnt how reality works.
Instead of looking for fault look at every single player, especially yourself, and try to figure out what you could have done better to contribute to a better ending. Every single person involved will have some way they could have improved their contribution in some way, but the idea of "fault" particularly when its concentrated to a single point (or very few points) will not get you to where you want to be.