Fire and Water… not a very promising combination. However, both Sagittarius and Cancer are guided by Jupiter, and because of this you two may in fact be compatible. It all depends on how you approach your partner, and whether you can find the right balance of adventure and emotion in your relationship.
You, dear Sagittarius, are a generous and protective partner. This is precisely what an insecure and sensitive Cancer needs in a lover.
However, this can be a bad quality, because both of you could end up too afraid to tell each other when you have a problem. You will do this out of a sense of protection, not wanting to hurt your partner. Cancer will turn the problems she has with you inward and get into moody, dark emotional moods. (The Crab has enough problems with mood changes, even more would make it over the top!)
Water tends to want to stay home, relaxing in comfort and peace. Fire would rather get outside and be active, meeting new people and enjoying the world. Fortunately, you are also a mutable sign, meaning you will be flexible enough to stay home when your Cancer really needs you.
However, if you decide to go out one too many times, Cancer may get upset for days, being thrown into one of the Crab’s famous dark moods. Don’t expect your partner to tell you what is wrong until weeks, maybe even months after the fact. This can be tiring to deal with.
Sagittarius and Cancer are both sentimental and emotional, so you may be able to understand when your partner gets upset with you. Although… your partner will be upset with you so often that your understanding and protecting nature will be stressed and stretched thin.
If you love your partner, this relationship could be full of passion and love, with a deep current of emotions running all throughout. If you two were not meant to be, you will find yourself tired and worn out dealing with the emotional Crab’s moods.