Are you compatible?
You are both dreamers and in love with the idea of love. Perhaps this is what you were looking for? You treat each other as equals, with neither attempting to control or dominate the other. However, you have many differences that can make your relationship difficult. Pisces is passive and Sagittarius is full of energy. Pisces is sensitive and Sagittarius forthright. Sometimes you're completely compatible and at other times you're totally incompatible.
Pisces loves to aid Sagittarius with their work, and each can supply what the other lacks. Pisces can also teach Sagittarius sensitivity and subtleness to a Sagittarius and in exchange learn better how to manage on their own.
You both tend to go to excess or promise more than you're really capable of and this can cause arguments. Sagittarius may trust Pisces far more than they deserve and can feel let down, as well as frustrated with Pisces refusal to move on. Sagittarius is straightforward and often hurts Pisces unintentionally, especially when they become impatient with Pisces' more relaxed pace. You both have blind spots and deception or self-deception can undermine your relationship if you aren't both as clear, precise, and honest as you can be.
You are fascinated by eachother. If Pisces allows Sagittarius the space they need, they will bask in the glow of Pisces' love. Sagittarius loves the deep connection they feel from Pisces and is intrigued with Pisces' seductive ways.
If you don't break up in the first few weeks, you have a good chance of staying the course. It will take some serious effort to make your relationship work long term, but both of you have the flexibility to make changes and the foresight to see the consequences of your actions, so long as you make the effort.