Einstein once said that the definition of insanity is doing the same thing over and over while expecting different results. Yet as scientists, we are taught to fundamentally question this assumption. We replicate and repeat with the express purpose of determining if a result is reproducible or merely the product of random chance. As social and emotional creatures, we do the same thing. We like to believe in second chances. We tell ourselves that stochastic circumstances are to blame when things don't go the way we imagined, so when presented with the opportunity to try again, we often do. Or, at least, I do. But no matter how logical an argument I can make for do-overs, Einstein was right. In retrospect, I feel like a fool. As I sit at the edge of my bed fumbling with my guitar, I can't help but blame myself. Why did I choose time and again to trust a person whose actions have always betrayed it? Blinded by love, I had a slew of reasons, a variety of parameters I could change that I thought might affect the outcome. But now, with 20-20 hindsight, I cannot find any. I should have known better, I chide myself. I failed the scientist in me. Yet still at the slightest mention of him, I flush with anger, jealousy and regret, and heart pounding, I fantasize about retaliation and justice. Evolutionary psychologists would tell me that the physiological experience of betrayal stems from the fact that humans, at our core, are a social species. Personal bonds were vital to our ancestors, and thus natural selection has reinforced emotional mechanisms that evaluate the connections we form with others. In a dangerous world, our ancestors had to know whom they could trust with their lives. Anyone who threatened the relationships we have with one another didn't just wound pride or break hearts, they threatened our predacessors very survival. The reaction is strong and visceral: stress hormones spike, leading to twisting pain in our gut and heightened sensitivity. But at the same time, areas of our brain involved in deception detection activate. While we feel the rush of cortisol and adrenaline clouding our thinking, brain regions like the anterior insula process our physical and emotional state to make judgements of trustworthiness to inform future interactions. My desire for retribution is primal, too. When we feel betrayed, our brains light up in areas associated with agression and testosterone levels rise. Scientists have found that other primates get upset when they feel that have been treated unjustly, and that people, when trust is broken, often will choose to punish the transgressor even if that punishment comes at a high cost to themselves. We want to lash out, to make things equal by returning the wrongs inflicted upon us. But instead of acting on instinct, I start to play. As calming notes pour from my fingertips, I feel the burning pain in my chest subside. If only my previous judgements had been more permanent. A friend of mine likes to say "monkeys learn," but clearly, I didn't the first time. Though the rest of our evolutionary lineage seems to be quick to categorize friends from foes, I could not. What's done is done, though, and I am left to collect the pieces of my heart that they shattered so effortlessly. While I might not have learned my lesson as quickly as I should have, I have learned it now. I know that this time is different. There will be no more replicates, no more re-runs with the hope of a different result. There are no variables I can change to get what I want. The data are clear, and it's time to stop trying to bias them toward the end I prefer. All that is left is to document what happened, so like a good scientist, I write and record my final results.