Varieties of regret: A debate and partial resolution, Psychological Review
Different interpretations of an apparent temporal pattern to the experience of regret were addressed through joint research. T. Gilovich and V. H. Medvec (1995a) argued that people regret actions more in the short term and inactions more in the long run because the sting of regrettable action diminishes relatively quickly, whereas the pain of regrettable inaction lingers longer. D. Kahneman (1995) disagreed, arguing that people's long-term regrets of inaction are largely wistful and therefore not terribly troublesome. Three studies that examined the emotional profile of action and inaction regrets established considerable common ground. Action regrets were found to elicit primarily "hot" emotions (e.g., anger), and inaction regrets were found to elicit both feelings of wistfulness (e.g., nostalgia) and despair (e.g., misery). Thus, some inaction regrets are indeed wistful (as Kahneman argued), whereas others are troublesome (as Gilovich and Medvec maintained).
Thomas D. Gilovich, Victoria Medvec, Daniel Kahneman
Gilovich, D. Thomas, Victoria Medvec, and Daniel Kahneman. 1998. Varieties of regret: A debate and partial resolution. Psychological Review. 105(3): 602-605.