Both the signs have great differences in nature. Without good communication cancer will be isolated because Sagittarius is far too wayward and freedom-loving.Sagittarius is mentally, emotionally and physically independent which can make Cancer feel insecure. Both are generous in different ways, Cancer tends to cling, which causes Sagittarius to feel smothered or trapped. When this twosome first meet, they can have a terrific time together..They'll think they have made it. But almost from the moment they tie the nuptial knot, the rot will set in.