I learned this aphorism from my book of aphorisms.
시어미에게 역정나서 개 옆구리 찬다
si.eo.mi.e.ge yeok.jeong.na.seo gae yeop.gu.ri chan.da
mother-in-law-DATIVE anger-happen-SO dog flank kick-PRES
[She's] mad at the mother-in-law, so [she] kicks the dog.
This means the same as "shit rolls downhill," I reckon. It's the idea of the pecking order, or the food chain, or whatever you want to call it. The traditional Korean household is hierarchical, and the mother-in-law outranks her daughter-in-law. So the daugher-in-law has to maintain the utmost respect and deference toward the former, and when she's mad, she has to vent her anger elsewhere. Poor dog.
[daily log: walking, 6.5km]