You're a reliable and supportive lover to this person, and they definitely appreciate the fact that you're their rock, their safe harbor. They come to depend on you to be there for them when times get tough, and they appreciate the sense of structure that you lend to their life, especially if they're used to a more freeform or even chaotic lifestyle. While you may not think that's an exciting or romantic enough quality, it's actually a wonderful one, and it forges a bond between you that could easily last long-term.
You're willing to be this person's teammate, and so they return the favor by being yours. You give each other your best advice and take turns motivating each other, when needed. You bring your own knowledge and experience to your lover's life, to offer them good, solid advice and guidance. Of course, the kind of security this aspect promotes could also lead to a certain complacency. You might come to trust one another so much that you grow lazy together, and don't face the serious things in life at all! Just make sure you keep each other's eyes on the goal, and you can get the most out of this aspect.