I am Pisces, My Lover is Sagittarius
This can be a tough match, if only because Sagittarius are so direct, and Pisces are so diplomatic in the way they approach communication. Your Sagittarius can come across uncaring, too blunt, and even deliberately hurtful. When confronted with these feelings, Sagittarius may respond by saying, "Well, you asked, didn't you?" Arguments go around and around on this topic between Pisces and Sagittarius and can eventually kill the relationship. Sagittarius is a fire sign and Pisces a water sign; therefore this match is not compatible by classical astrological standards.
What you will appreciate, though, is your Sagittarius' love of education and his or her penchant for deep philosophical discussion of a wide range of issues concerning the human condition. You will also adore your partner's need to travel far and wide. However, your tendency to worry will bewilder your optimistic Sagittarius, and you'll wonder how he or she can maintain such an outlook in the face of terrible odds. This could irritate you, as will Sagittarius' criticism of your flaws.
Your partner has an athletic bent, something which Pisces lack. Perhaps your Sagittarius can interest you in working out at the gym, so you can shape up and get fit. Or you could interest your partner in more gentle-to-the-body sports, such as swimming. Anything too strenuous or competitive will probably turn you off. Perhaps you two will agree not to participate in sports together but to do other things instead.
Sexually, Sagittarius are playful and humorous (a plus), but your lover may lack the emotional intensity you crave. If your Sagittarius doesn't make less-than-funny jokes during lovemaking like, "Am I dreaming or are you gaining weight?" you might be able to continue the relationship. Just be prepared to let some of the typical Sagittarius commentary roll off your back.
Sagittarius is known as the bachelor sign, so be forewarned. Freedom is very important to Sagittarius. Sagittarius have a deep psychological need to avoid having to "report" to someone else, and this is what makes them worry about commitment. In fact, they're often quite loyal. Pisces is not always into commitment either, so this relationship may work for you. On the plus side, both of you are mutable signs, which means you are flexible people at heart. Intellectually, you really hit it off with Sagittarius. This match takes work, because you must turn the other the other cheek when your partner becomes too blunt. If your union succeeds, it is because you have been willing to put in a great deal of effort.