Two people able to form a long term relationship often have a lot in common, or they find things they can share. For those who have grown up in the same type of household, it is easier to find compatibilities. They might like the same type foods, agree on the same living arrangements, and they might even share a common religion. Those from very different backgrounds have a tougher road to follow if they want to remain together.
It might seem many issues are just on the surface, but couples who have not grown up in the same area often find these supposedly superficial differences to be roadblocks. While it would seem religion would be the largest, food or even living arrangements can be the most difficult to overcome. Setting aside their differences does not always work, so couples determined to spend a lifetime with each other must find or create common ground.