Regret

An emotion that arises upon appraisal of the consequences of one’s decisions. Like disappointment, regret is a ‘post-decisional emotion’. Regret is an emotion that arises when there is a perceived gap between the factual outcome with an outcome that might have been had one chosen another course of action. As such, regret arises when one’s outcome is compared with ‘what I could have chosen instead.’

Reference:
Zeelenberg, M., van Dijk, W. W., Van der Pligt, J., Manstead, A. S., Van Empelen, P., & Reinderman, D. (1998). Emotional reactions to the outcomes of decisions: The role of counterfactual thought in the experience of regret and disappointment. Organizational Behavior and Human Decision Processes, 75(2), 117-141. doi: 10.1006/obhd.1998.2784