Humans are complex creatures, and relationships between them get pretty complex as well. Some things you should accept, others - do something about. For one couple, fighting and breaking up every evening to make up every next morning is fine, while the othersuffers from it without speaking up. One thing about the job is just how the way things are, while another unhealthy yet stuck due to neglect or a certain level of apathy.
Where's this line? I get the feeling that, despite the vastly different subjects, it's stays the same or similar: this is fine, but this next step is towards hell, so you better turn around.