5. Common values
It is not possible for two people to have absolutely the same set of value systems as there is always a distinction between the past life experiences they had or the way they are brought up.
If you have almost the same set of values, ideologies, and beliefs, half of the battle is own; for you both are on the same side.
Differences in value system may lead to constant arguments, fights, and complains that will gradually lead to toxify your relationship, leaving you to ultimately quit it.
If love would be sufficient enough for a relationship then half of the divorces would have never materialized.
To nurture love, it needs fertile ground to grow on.