“’We’re like family here.’

It’s a line that seems enshrined in the collective unconsciousness of American workers. We spend more than 2,000 hours per year with our co-workers, so it seems only natural that we should think of them as family. We celebrate birthdays together, honor anniversaries, hang out at happy hours … these people are like a second family. Right?

Not necessarily, says Alison Green, who runs the career advice blog Ask a Manager and whose latest book, which has the same title, published earlier this year.

“There’s nothing wrong with loving your work, enjoying your company and having good will toward your co-workers,” Ms. Green told me. ‘We all should strive to work in jobs like that. But it’s still O.K., and even good, to put yourself first in the long-run.’”