What the stars say about Sagittarius and Capricorn
Sagittarius wants to expand to the hilt, boundaries are anathema to it. For Capricorn, on the other hand, boundaries mean security. Tolerance on the other hand - a main virtue of Sagittarius - is interpreted by Capricorn as weakness. And for Sagittarius, too much order - a main principle of Capricorn - is life-denying.
In almost all cases, this combination amounts to a duel between drive and inhibition: the typical Sagittarius needs goals, something to move toward. He needs to keep moving because that is his primal motivation, through which he finds himself and can "stay with himself." A true Capricorn, on the other hand, regulates everything and sets binding standards. He has to know exactly the result beforehand in order to even begin with an action, while the Sagittarius first gets going, pursues his goal and then will already find out what the result will be. It is a colossal contrast, which usually results in neither Sagittarius nor Capricorn feeling sufficiently accepted (loved).
So it is not easy with the two, although they live "door to door" so to speak. But there are also good reasons to dare a relationship: The serious Capricorn benefits from the humorous nature of Sagittarius, vice versa, Capricorn helps the other to stay grounded in reality. The common path to the center then consists of Sagittarius contributing his ideas and Capricorn checking them for feasibility.