Your partner ends up feeling dissatisfied with the way you two connect emotionally -- or with the way you fail to connect. This may not be apparent at first, but over time, they start to realize that you just don't speak the same language emotionally. They seek a certain level of security that you just aren't able to recognize or support.
They want to make a real and satisfying emotional connection, but that's difficult because you are always trying to control them emotionally. Where they want simplicity and easy comfort, you want intensity and magnetism -- and could even resort to manipulation to spark those feelings! They end up realizing they just can't get as close to you as they thought they would. Trust is an issue between you due to this troublesome aspect; your lover grows so used to having their feelings hurt and defending themselves that they might forget how to relate on a normal, uncomplicated, positive level. If either of you wants this relationship to last, you both have to make some adjustments in what you expect of the other on an emotional level. Gradual compromise and getting to know each other as the people you really are, rather than whoever you might wish you were, is key in making this work.