Why? Helps you clarify who you are, who you aren't, what you are for, what you are against. It also illustrates that not everyone is on your side. There are people and forces that must contend with, people and forces to navigate around and thru. The world is an amazing place, but it's not all for you. So many competing interests and forces. And enemies? There is that Biblical hard bit of advice: "But I say unto you, Love your enemies, bless them that curse you, do good to them that hate you, and pray for them which despitefully use you, and persecute you."
I don't know, that is a tough cookie to crumble. But maybe we can love what our enemies teach us? You know, lessons? They show us what not to do, what not to be. Maybe we can use them as mirrors, to see our own flaws, inconsistencies, dark moods, and bad acts? Point us the way to do and think better?