Clarification of the phrase "marriage is hard"

I had a conversation with a friend who recently got divorced. She was telling me all these things that went on in their relationship that I just couldn't believe. I asked her why she stayed so long? She responded with well everyone says "marriage is hard" so I figured that this was how it was supposed to be. Disclosure* my marriage is not perfect nor am I*. BUT I wanted to clarify for those who maybe have not had examples of healthy marriages. Yes, marriage is hard but your relationship shouldn't be. Life is complicated and when two people from different backgrounds come together to make a new life it inherently presents challenges. It's those situations that make marriage "hard". There has to be compromise and change BUT the person you are with should make all of those challenges EASIER. You should ENJOY going through changes with them and creating a new life that centers around the two of you.