You'll have a grounding effect on each other's thinking. Working together, you'll be able to make more rational decisions than you might on your own. You'll keep each other well within the bounds of logic, and you'll rarely try to take on impossible tasks.
Therefore, you'll be able to plan well together, and if your relationship is a long-term one, you're likely to make good investments as a team. The projects you undertake together are likely to be successful because you'll be so strong in the planning stages. Your communication during disagreements will also be grounded and sensible, which will help you work together through any problems that come up during the course of the relationship. Just make sure to continue challenging yourselves and each other at an intellectual level. Don't be afraid to take risks or mental leaps. Creative thinking is every bit as important as reason and consistency. And don't forget the importance of passion! If you're too calm and reasonable with each other, you might forget that there's a lot of love and energy between you.