Responding to emails during off-work hours isn't the only area in which you need to set boundaries. You need to make the critical distinction between what belongs to your employer and what belongs to you and you only.
Walmart isn't your average mom-and-pop operation. It's the largest employer in America. As such, it's the trendsetter for millions of other employers of low-wage workers.
There would be no idling in a co-operative workshop. Each workman, being an employer, has a spur to his own industry, and has a pecuniary reason for being watchful of the industry of his fellow workmen.
When you do a writing job for a studio, one of the things you want to do is satisfy the expectations of your employer. That's a little bit different than when you sit down and write something to satisfy yourself, because then you're the employer.