When you get together with this person, you are driven by a sense that you have some important work to do together. What this work entails is up to you -- it could be of a personal nature, such as building a good, solid relationship that leads to a long-term commitment and establishing a family; or it could be a business venture that requires both partners' careful forethought, planning and hard work. You work on a project together, and you encourage your partner to work harder and better than they would have on their own.
This aspect lends a grounding effect to your relationship. There is a sober feeling to your bond, and though this doesn't have to be a restrictive influence, your partner might feel dissatisfied under its influence. For a business relationship, sober energy, focus and hard work are fine, even desirable. In a romantic relationship, though, they want a little bit of lightheartedness, of freedom and spontaneity, even foolishness. They don't want everything always to have a purpose or a goal; sometimes they just want to lie back with you and enjoy the bliss of the moment. This is probably hard for you to do with them. You just naturally focus on the more serious side of life, and your responsibilities and your commitment take center stage. You're likely to be in it for the security above all else, which can make your combined social life seem superfluous or stilted to your lover.