Occupational Slumming

Taking a job that is beneath a person's education or skill level as a means of retreat from adult responsibilities and/or avoiding possible failure in one's true occupation.

Although he was trained to be an architect, Hank took a job at Burger King instead because he didn't believe he'd be able to design a building that anyone would be interested in financing. His parents were disappointed by Hank's obvious occupational slumming.