As a dog returns to its vomit, so a fool returns to his folly (v11).
This verse has come to my mind many times. Whenever I keep doing the same dumb thing, or keep slipping up on the same issue, 'canine chunder' comes to mind.
Dogs seem to like inspecting, even eating, their own vomit, it is truly disgusting. They have no concept of how gross it is.
I sometimes wonder that if I could see how repugnant to God my own sin is, would that stop me returning to it? I don't know, bit I do know I need to grow in my revulsion to my own sins.
Vomit is a good metaphor for folly ... and the cross is a grace filled reality for serial sinners like me.