From my “Murphy’s Law” desk calendar archives thanks to Aunt Evelyn, Uncle Pipey, and cousin Nancy:

McClaughry’s Codicil to Jone’s Motto: To make and enemy, do someone a favor.

Goofy guy’s extrapolation of  McClaughry’s Codicil to Jone’s Motto: The extent of the enmity is exponential if the new enemy is a score keeper.