How do differences between souls come about?
When souls come down to this world to do the will of the Creator, they descend in gradual progression through the spiritual worlds, which generally divide into the categories of Atzilut – Emanation, Briah – Creation, Yetzirah – Formation, and Asiyah – Action. Although all souls pass through all the worlds, some pass through some worlds simply as a way-station, and some pass through some worlds in a manner of ‘enclothement’—becoming unified with its characteristics.
It can be compared to two people who set out on a trip around the world—one of the travelers stayed awhile in each place, became acquainted with the inhabitants, learned their language and customs etc; the second person didn’t delay in most or any of the places. Thus although both of them were actually in the same places, the experience was different and had a different effect on each of them.
So there are some souls which go through a process of ‘enclothement’ in the world of Briah – Formation, undergoing a G dly experience there, and then hurrying through the rest of the worlds on the way down, and others make their stop in another world, and so forth, and this is how differences come about between souls, despite their coming from the same original source.