dogpiss means your bad or dogshit at something but worse than dogshit

When you eat dirt for the first time and leave your family to build a shack in the woods

Essentially it’s the polar opposite to phrases that use the word “Piss” to imply something is easy such as “Piece of piss”, so Dog Piss would be used to say that something is hard or difficult. It’s related to the phrase “Dog Shit” in the sense of conveying negativity.