A) what a dog does with anything it can't chew or play with
B ) a variation of 'spit on it and walk away': walk away, from any experience, even a negative one, with your head held high and move onto bigger and better things, rather than let said experience frustrate you.
A variation of ' piss on it and walk away' meaning, walk away from any experience, even a negative one, with your head held high, and move onto bigger and better things, instead of letting the negative experience frustrate you.
In terms of anger management adapted to modern society, spit on it and walk away is a good piece of advice; do not turn your frustration and anger into violence.