No one ever claimed that raising a child was easy. Babies are completely reliant on you and need a lot of care all the time. It's stressful! Debates on techniques and methods cause divides in many a relationship.
That's why discussions are so important. Even then, though, they're imperfect. One couple made a compromise regarding changing diapers before they had their first child, but when one half started taking that compromise for granted, it resulted in quite the fight.