This person is a reliable and supportive lover to you, and you definitely appreciate the fact that they're your rock, your safe harbor. You come to depend on them to be there for you when times get tough, and you appreciate the sense of structure that they lend to your life, especially if you'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.
This person is willing to be your teammate, and so you return the favor by being theirs. 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.