Having a job that requires you to be “on” all the time is something of a badge of honor in today’s tenuous economy. It’s also incredibly unhealthy. There’s one behavior in particular that a new pair of studies found ruined the next morning for workers on the job. Using a smartphone to answer work emails after 9 p.m. led to people feeling less well-rested, engaged, and focused the following morning. In the first study, researchers from the University of Florida, Michigan State University, and the University of Washington surveyed 82 mid- to high-level managers enrolled in MBA classes first thing in the morning and late afternoon over the course of 10 days. The ages were varied, but nearly half fell between 31 and 40 years old. In the second study, the same researchers from looked at a more diverse sample of 161 employees in a variety of industries.