If you're attracted to each other, that fact alone indicates that there are plenty of positive aspects between you, because this one makes things pretty difficult when it comes to relating naturally as a couple. There is an element of control coming from you to your partner that makes it hard to get along. When you're together, they feel restricted in their romantic expression toward you, and it could come out cold or just stilted.
You try to restrain their natural way of being in a relationship. They could start to feel as if any affectionate advance they make toward you is rebuffed as inappropriate in some way. Needless to say, this makes it hard during moments when losing yourselves would be appropriate -- when you're being intimate, for example, or just out and supposedly having a good time. Your lover could even begin to feel as if any romantic overtures are made fun of or just flat-out denied. Where does this come from? You should both look at the experiences you've had in your lives with all kinds of love -- relationships you've each had with your fathers, for example, or with past lovers. You may have experienced this kind of coldness and lack of affection before, and somehow, when you two get together, those old feelings from past relationships are stimulated. If this relationship is long-term, facing this problem and getting through it is important.