Why do people fight so much in relationships?

i notice that people who love each other fight a lot, because they are to used to each other and need to get away sometimes. take my mom and my step dad for example, they fight more than ever!!! other wise sometimes people just fight because both people refuse to communicate, and sometimes a certain person can be stuck with their ways and don't want to change their ways, and the other person can be like that to.

However, if you are in a relationship with someone who is physically abusive (regardless of whether the abuser is a man or a woman), please leave that relationship; this kind of "argumentation" is not normal or safe.