The 3 Karmas in Analogy

A simple analogy is: 

The granary represents the Sanchita Karma; that portion taken from the granary and put in the shop for future daily sale corresponds to Agami; that which is sold daily represents Prarabdha.

Here is an analogy taken from Vedic literature. 

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.

Sanchita, the vast storehouse of yet unseen impressions  

Agami, those currently in front of us to decide or act on   

Prarabdha, consequences already playing themselves out 

Similarly, there are three kinds of arrows:

Quiver: Arrows in the Quiver (Sanchita karma)

Hand: Arrows in Hand (Agami karma)

Flight: Arrows in Flight (Prarabhda karma)

This is a very practical tool: The metaphor of the arrows is a practical tool for daily life. The mind easily recalls the visual imagery, which serves as a reminder to do a good job of "shooting the arrows" of actions, thoughts and speech. 

Decisions: The quality of our decisions leads to the quality of our actions, which means the level of our archery ability. 

Consequences: The aim of the arrows also determines the quality of the consequences that come back from those actions. 

Deep impressions: Those consequences come to rest in the bed of our subconscious as deep impressions (Samskaras) which determine our Karma. 

Recycling: These Samskaras will at some point lead to further thoughts, speech, and actions, that again lead to more consequences, with cause there is always effect.