Because you two don't match up in your emotions, values and interests, you both feel as if you have to either repress your true personality when you're together or withstand criticism of things about you that are inherent to who you are. You are just out of sync on a variety of levels, and if either of you tends to be critical, or if other aspects between you indicate that as a potential problem of this relationship, you will probably have some arguments over a variety of subjects. You are rarely in the mood for intimate play at the same time; you might not even be in the mood for the same kind of movie or restaurant or anything else!
That's true of a lot of couples, of course, because people are different from each other, and when you're looking for love, you aren't looking for your twin so much as someone who adores you, and all the unique qualities about you that make you who you are. In this relationship, that's just what you two might lack. Sexually, you could be quite out of tune, having some very different ideas of what's hot and what's not. You might get your feelings hurt when your advances are rebuffed or your sensual imagination is stifled. Misunderstandings are the name of the game unless you both put plenty of energy into working together. Communicating clearly and exercising your utmost patience in dealing with each other helps, but it takes effort.