The desire that we need to rise above is as great as the Light that created it in terms of volume, depth, breadth, energy, and might. We are not able to correct it alone. For this reason, the Creator divided it into multiple parts so that each of us would have an opportunity to correct our individual part in this immense desire. As a final result, all parts come together.
At the same time, Kabbalah relates that we were separated in order to learn to rise above our hatred (separation) and love each other so that we would learn to love the Creator in the same way. That is, the purpose of our division into individual souls is to raise in us a new, caring attitude to others, not to make our work with the will to receive easier.
Both assessments are correct. The purpose of our separation is two-fold. We must attain love for others before we attain love for the Creator, as it is written, “From love of others to love of the Creator,” and the division into multiple parts makes our work toward the correction of the ego easier.
Actually, the Creator could have created two Adams instead of one so that they would learn how get along with each other. We have heard that the “minimum quantity is two,” so two would have been enough to learn how to step outside oneself toward the other. Still, the Creator divided the collective desire into the multitude of souls of mankind according to the density or mass of the egoism so that each of us could correct his individual part of the collective ego, restrict it, rise above it, and use it in order to bestow onto others.
Therefore, our work in correcting this massive ego is divided into multiple parts relevant to the number of souls (or people) in our world. Hence, the population on earth decreases or increases to match the density of egoism in this world at any given moment.
Beside the fact that this work is divided between a great many people living today, it gradually gets completed by each of us with every return to (reincarnation in) this world. Each time, we correct our ego in small portions, day by day, during our entire lifetime and multiple incarnations.
From Mega Congress Lesson 1, 7/23/10