look at my own arse when I shit

When you are that busy, that you don't even have time to look down when you are having a shit because you are too focused on something, you have to take it into the bathroom with you and use the toilet as a temporary office
Extreme measures involve having to wipe without even checking the state of the tissue before flushing it.

'I had that many emails coming through that I had to reply to, I didn't even have time to look at my own arse when I shit.'

own up to my shit

When someone mocks you for not putting a price tag on the foreign objects you leave behind in the toilet it's art some might say, or when you frequently don't flush the toilet and someone notices your master piece. "Hey Sam I've been noticing you've been leaving behind presents in the works toilet 🚽 do you mind flushing it, it stinks." "Of course after you walk across Lego pieces and glass shards we'll have a deal pal."

own up to my shit action, verb, adjective should take part of owning up to your responsibility whether it's physical or imagery.

Rather eat my own shit

Used to express that you really don’t want to do something.

Are you going to the football game? Hell no, I’d rather eat my own shit.