Reality vs. Identity/Ego

If you have lived your whole life one way, and then you are told that it was all a lie (not true), your mind can't handle it because your whole identity (your mind) is based on that lie. And all the efforts have been for nothing, all the investments amount to nothing and you'd have to start all over from scratch. So you have a choice to make: to either accept it or to violently oppose it, because the investment is too great to let go, you are too attached to it (It is all you have, because that is your whole reality, your entire life. So essentially the question is: are you ready to die?)

The latter is what you see with fanatically religious people: they would rather kill the one pointing the reality out than let go of the delusion. But to succeed with this you'd have to kill the whole universe to be right, because you are fighting the reality after all.

Holding onto your ex/oneitis is the same deal: You have invested too much to let go, too much to accept the reality that he/she didn't feel the way you did, that was all for nothing, that you weren't that important. But keeping investing more to bad investments doesn't make them good investments. Accept the losses, move on.

tl;dr: Are you more than just your memories and beliefs? (which are just thoughts and assumptions) 

Is there more to you than you think, is there room for growth? 

Or are you going to sit in the corner you have painted yourself in and defend it to bitter end?