The ego lives either through bad sanskaras or through good sanskaras, or through a mixture of good and bad sanskaras. Therefore the emancipation of consciousness from all sanskaras can come either through the good sanskaras balancing and overlapping the bad; or through some good sanskaras balancing and overlapping the bad, and some bad sanskaras balancing and overlapping the good.
If a dish is dirty you may cleanse it by covering it with soap and washing it with water. This is like good sanskaras overlapping the bad.
Now if the dish is full of grease, one way of getting rid of the grease is to cover it with ashes and then wash it with water. Ashes are one of the most greaseless things in the world and, in a sense, the opposite of grease; so that when ashes are applied to the dish soiled with grease, it is easy to cleanse it. This is like bad sanskaras overlapping good sanskaras.
-Extracted from “Discourses”, 7th Ed, p65