I am Sagittarius, My Lover is Cancer
Can a Centaur (you) and a Crab (your lover) make things work? This is a hard relationship, but with some effort, you might get it working well. It won't be easy. Let's look at the obstacles.
Fundamentally, you come at life through different doors. Your lover is a water sign, highly emotional and moody. A Cancer in a bad or depressed mood for days at a time could be hard on your nerves. You, on the other hand, are a fire sign, an element that does not mix well with water. Being a mutable sign, you are more flexible than your partner. You could find your lover's hesitancy to deal with change puzzling at best, and irritating at worst. You keep your vision trained on the future, while Cancers like to look back. This would be all right, if only they didn't engage in "I coulda, shoulda, woulda" so frequently when looking back on events. You don't feel this serves any purpose, and sometimes you are right.
On the plus side, your Cancer will nurture you from the depths of his or her soul. Cancers are excellent listeners and will pay careful attention to what you say, offering their sound advice at the end. You will know your Cancer loves you -- few signs give as much in a relationship as Cancer. Cancers are slighted easily, so watch your Sagittarius' penchant for brutal honesty; it will bruise your tender Cancer's soul. Once you blurt something out that's hurtful, it is impossible to take it back; Cancers, of all the signs, will remember what you say forever. Cancer has the memory of an elephant.
Sexually, Cancers can bring lovemaking to heights you have never experienced! Be careful not to take this intimacy with your lover too lightly. This is no casual affair to him or her -- still waters run deep. Cherish your Cancer. The love you receive in return will astound you.
In all, this is a hard relationship to make work because of the differences in your temperaments. But it is possible if you give each other lots of tender loving care.