There are many people who have dealt with far worse than a breakup. Some have lost children, parents, spouses... they manage so you will too.
Most of us have experienced the pain of breakups or other kinds of doomed relationships. Not to make light of those feelings, but consider: at least those you love(d), though no longer with you, can at least be thought upon fondly and wished-well in their lives.
There are worse things than a breakup with someone. Learn to be happy without them, and happy for them if they choose to move on without you. There are far worse alternatives.