Even if you are mad at someone you love, you should try your hardest not to speak with hostility towards them. Because the first fight is always the most painful. Everyone knows that. And during that first fight, you might call eachother names, or make painful accusations. And once you guys kiss and makeup, it seems normal. And the next fight comes easier because you think it's okay to turn to those words and actions when frustrated. And while the first fight may have seemed okay at the time, fights begin getting closer together, and more hostile in nature, until it is an everyday screaming match, because you've gotten in the habit of being so cruel when angry. If you love someone, don't get into the habit of being mean to them while you are mad. Keep a level head, and choose your words carefully. Being mean or impatient with your significant other can cause the toxicity level in a relationship to skyrocket very quickly.
