It takes a lot of experience of life to see why some relationships last and others do not. But we do not have to wait for a crisis to get an idea of the future of a particular relationship. Our behavior in little every incidents tells us a great deal.
Sometimes you take a job for the money, sometimes you take it for the location, sometimes you take it for the script; there are just a number of reasons, and ultimately what you see is the whole landscape of it. But I can tell you from behind the scenes - that's what it is, as an actor.