The thing is.....let's just imagine Eric & Nicole being happily together at last. He has been a priest, very religious, and Nicole......well, she is not.
So, when the initial "how great we are together at last, isn't it wonderful" phase wears off, what happens when they have to deal with life? They are going to react differently to things people do, say, events, snubs, cross words (by other people to them) and will argue about it.
I just keep remembering how Marlena was constantly trying to alert John, and Brady, to the evil Kristen was doing and they refused to pay attention.
I do hope, that despite how Nicole feels about Eric, she recognizes that in the long run, he would make her very unhappy. Just as he has the past few months.