Yes, I think that unrealistic expectations often play a part in relationship breakdown and divorce. Whether they are "fairytale-like" or not, expectations can threaten marriage.
My favorite fairytale was Cinderella and I suppose I always yearned for my prince to whisk me away to a castle in the clouds. But I saw too many real life marriages that weren't "happily ever after" and they did NOT end in divorce so I guess I expected there to be bumps in the marital road.
Friends I know DO have unrealistic expectations and have divorced because of them. One woman divorced twice after the initial thrill is gone. She equates love with the thrill of infatuation, never staying long enough to experience deep, satisfying, devoted love. Another woman thought that marriage meant both partners would be blissfully happy doing everything together, compromising with a smile. She interpreted his wanting separate time as incapatibility.
My husband and I are not completely compatible and that has caused us to work a little harder, not at being more compatible, but at being more accepting that it is okay to be very different and still love and respect each other. We finally realized how harmful it was to expect to achieve some "ideal" when neither of us is an "ideal" partner. We settle for the wonderful achievement of still liking and loving each other--most of the time.
