That can hurt a lot, even if you’re doing the breaking up. Everybody handles that differently, but general advice is to take extra good care of yourself for a while: good food, good sleep, whatever else makes you feel taken care of. Maybe resist the urge to do a rebound relationship for a bit, unless that’s what you need. Give yourself some time to be sad, or angry, or to feel any other way you do. No really wrong answers here, and none that don’t at least sorta suck. Be well, I’ll be here.