It can be a hugely stressful situation when you lose a person that you truly love to another.  You can go crazy delving into your emotions, wallowing in self-pity or obsessing over what you could have done differently.  What you need to do is  deal with your emotions honestly soon after the breakup and not avoid the issue.  Instead, put your energy into studying a resource on how to get your ex back so that you can plan what to do, or at least figure out if the person is indeed the love of your life and worth the effort.