In vedantic literature, there is a beautiful analogy.
The bowman has already sent an arrow and it has left his hands. He cannot recall it. He is about to shoot another arrow. The bundle of arrows in the quiver on his back is the sanchita; the arrow he has shot is prarabdha; and the arrow which he is about to shoot from his bow is agami. Of these, he has perfect control over the sanchita and the agami, but he must surely work out his prarabdha. The past which has begun to take effect he has to experience.