We all come across doting or lovely or egoistic or misunderstood couples, on whom we make guesses on who will stay together forever and who will NOT last and break up somehow.
I have a friend who fell for a boy who seemed alright at first but then revealed out to have a serious drinking problem, which everyone except my friend knew. He kept lying to her about this, and she trusts him for some reason. So somehow my intuition says that they won't last together, even though I want to see her happy with him.
Likewise, have you ever looked at some couple and got that feeling?