Two people should not be complete opposites of each other (nothing in common; too much conflict)

Two people should not be exactly similar (too much in common, not enough conflict). A little bit of conflict is good. The differences in personalities prevent stagnation and complacence.

Both situations would drive both people crazy. A little both of conflict and differences is needed. But where conflict does arise, each party should be able to back down and compromise sometimes.

Not a fan of "agree to disagree" either. To me, that's just putting a lid on discord and saving it for later. Having two non-compromising opposite opinions without a hair of agreement in between sounds like both sides are too stubborn to see the other side.

One person can't just always be a follower, a yes person. It can be tiresome when someone doesn't have any preferences and just goes with the other person's choices all the time. (I'm making you pick the restaurant; I'll pick the hotel)

Well, that's enough rambling. Maybe I should write a post about it :-)