The old rebbe explains in the 29th chapter that sometimes the “benoni” would feel that his heart is “closed up”, and he cannot pray normally with a passion, and so he will not be able to fight his bad instinct. This is become the bad covering the light of the G-dly soul, and doesn’t let it affect the heart, even though he understand G-d’s greatness. Still It doesn’t come from the brain to the heart, so he should feel it, because of the bad. Therefore just like a log of wood which the fire doesn’t catch on it, you break it to smarter parts. So too here, a body which the light of the G-dly soul doesn’t affect it, you break it.