You'll have trouble synching up your energies, desires, goals and ambitions. Just when one of you is feeling 'up,' turned on and raring to go, the other will withdraw, feeling low-energy and turned off. This could take a lot of steam out of your sexual connection, but it will also get in the way of day-to-day activities and simply getting along as a couple.
You'll have such different rhythms that you'll find it hard to catch each other in the same mood at the same time, and this could become especially challenging if you're together long-term. When projects come up that you'd ordinarily tackle as a couple, you may have to accept that your partner simply won't be there to assist you as you might wish; and they'll have to learn to accept the same thing about you. You'll often have different ideas of how to go about things, as well as different levels of interest. This relationship also runs the risk of becoming imbalanced in terms of pursuer and pursued; one of you may fall into the role of giving out lots of affection, while the other makes demands and fails to give as much as they receive. Whatever happens between you, try not to bottle up your feelings, as doing that will only make things worse.