Aries and Pisces are very different as people, very different in their energies and in what they need in life. Aries is a fire sign. Pisces is a water sign. Even in the real world, water often puts out fire. I say this only because the motivation of the Aries is to experience life as an adventure, to experience the spontaneity and the joy and the curiosity and the wonderful movement that life is.
Pisces, on the other hand, is looking for something that is very deep and intensely bonded, that is creative in many ways. Pisces is drawn to the world of art and artistry and creativity, and Pisces is a dreamer. So we have Aries as the doer, and Pisces is the dreamer. If they can work that out, then they have good auguries.
In general, however, they have to go through a number of rough patches as they try to work this out, because Pisces can also become very clingy and needy. Pisces needs a lot of proof of love, a lot of affection, a feeling of being safe. Aries wants to be the adventurer who attracts attention and who experiences life to the fullest. In general, they can be good lovers. The relationship can last, but there are going to be a lot of temperamental differences between the two.