Breaking up is, indeed, hard to do. But according to researchers at Cornell University, certain breakups are more difficult than others. 
The team looked at four previous studies and determined that comparative rejections (rejections in which a person leaves to be with another partner) are more emotionally difficult than noncomparative rejections (breakups that don’t involve a third party). They discovered that comparative rejections do in fact feel worse, which was in line with their initial hypothesis. “This may be because such rejections lead to an increased sense of exclusion and decreased belonging,” authors Sebastian Deri and Emily M. Zitek wrote in their abstract. 
To recap: If your partner leaves you for someone else, you’re more likely to feel excluded, and you’re probably going to have a tougher time recovering. Of course, this is not too surprising to anyone who’s experienced—or maybe even imagined—this type of rejection.
However, they also found something surprising.
“Furthermore, we found evidence that, by default, people react to a rejection as though it were comparative—that is, in the absence of any information about whether they have been rejected for someone or no one, they react as negatively as if they were rejected for someone,” the authors wrote. In other words, if your partner leaves you for another person, you feel bad, but if they leave you and don’t indicate whether they’re entering another relationship, you’ll feel just as bad. 
And the breakup pain is real; you’re not imagining it. In one 2011 study, scientists showed study participants pictures of their exes, then asked them to think about their rejections (yes, it was a pretty cruel study). The scientists monitored the volunteers’ brains and found activity in the secondary somatosensory cortex and dorsal posterior insula—two parts of the brain associated with the sensation of physical pain.
Fortunately, science can also tell you how to deal with a breakup in a healthy way.
A 2015 research article authored by Grace M. Larson and David A. Sbarra investigated “breakup-related recovery,” observing a group of young adults whose relationships had recently ended. One group of participants would complete four visits with “multimethod assessments,” which forced them to reflect on their relationships. The other group of participants undertook a much less intensive set of assessments. 
According to the paper’s authors, the group that regularly measured their condition recovered relatively quickly, experiencing “decreases in breakup-related emotional intrusion, loneliness, and the use of first-person plural words when describing the situation.” As Larson told NPR, the research questions “helped [the participants] develop a stronger sense of who they were as single people.” If you’re going through a breakup, regularly reflecting on the end of the relationship seems to actually help you deal with the pain. Of course, you don’t want to wallow in misery, but focusing your attention on your self-development can help. 
Keep defining who you are as an individual, and the science says you’ll see improvement. “When a relationship ends, that really messes with your sense of who you are,” Larson told NPR. “You may think, ‘Who am I now that I’m not Mike’s or X or Y’s girlfriend?’ … I think that it’s possible that coming into the lab and answering these questions reminded them of their new status as singles.”
