I'm only allowed to eat or take a break after I finished the current goal. Yes, I set myself work goals like, I have to clean up half of the panels of the page, or I need to lay down the basic colours on all the characters, etc.
See, I have this tendency of working and forgetting to take breaks. So, I set myself small goals, where I have to stop after completing it and take a 30 minutes break. I also set up a timer, so I don't go over.