Marriage is hard. Even good marriages, happy marriages, peaceful marriages. You don't always agree and yet you can only move forward together. What's hard is figuring out the balance between protecting yourself and protecting the relationship.
It's this way for all relationships, not just marriages, not just straight partnerships, not even just between couples. That dilemma of knowing how and where to set boundaries, which of course requires you to know yourself; what you will let go and what you insist upon, what makes you feel good or distressed, what you've decided your priorities are regardless of the costs, and what you want most from those who love you and whom you love.
The dilemmas are not just about knowing the boundaries that you consider non-negotiable, but knowing how to set them in a way that produces the give and take that is needed to live with and love someone day in and out. Love is hard. Even strong love, lasting love, committed love.