Sudden betrayal is the worst. Because there was nothing leading up to it. There weren’t any clues. No hints. No signs. No foreshadowing. So when the shock finally hits you, all you can possibly think is “What did I do wrong?”
What did I do that could do to ever possibly justify this? Did I push too hard? Did I remain too distant? And in the end, the cluelessness you feel leads to the last possible conclusion. And that is that they never truly cared in the first place.
And the worst part? In a fair amount of cases, that last conclusion is usually the right one.
