Answer: If we could keep the achievements, then we would not be able to develop. If we constantly felt receiving the fulfillment, we would have considered ourselves in the state of final correction. My desire would be constant, the Light filling it constantly, and I would feel myself in the end of correction. How can I know what the end of correction means: 100 kilograms of desire and fulfillment or a million? If the Light fills my entire vessel, I feel satiated.
The newborn, who eats 50 grams of milk thinks that he has received a full meal. You need a kilogram to feel satisfied and he needs only 50 grams. Everyone feels himself filled in accordance with his wishes. If you fill yourself up to the end, then it is called the world of Infinity. Infinity means no boundaries: You received as much as you wanted without any restrictions and therefore this fulfillment is called infinite, unlimited.
Therefore, if we could keep the filling, then we would feel in perfect condition, in a perfect state and no need for further development.
From the 1st part of the Daily Kabbalah Lesson 7/18/13, Writings of Rabash