an idiom warning to be aware of ones vulnerabilities and limitations and to avoid self-sabotaging situations. The idiom draws inspiration from 'dont throw bricks in a glass house' and Jack Glasscock-- a 20th century American baseball player who himself coined the phrase 'Charley Horse'.
You're literally the most socially anxious person I know, I dont know why you keep doing these speed-dating events. You know what they say, Dont fuck rock pussy with Glasscock.