first,there has to be communication!having the same interests helps too!also,the same religion helps too!i mean if you are a different religion in can cause rifts and let's say you like animals and she doesn't it's going to be hard to never,say,have a dog!also,if you like swimming and she hates the water,she can't have tha same joy of going to the beach!it's those little things that make a relationship last!