July 11 (UPI) -- "My dedication was questioned." "Managers or upper management have looked down upon taking time off." "People think that maybe you're not as invested in the job, that you're shirking your duties or something." These are just a few of the responses to questions I asked during a study I conducted on vacation guilt among American workers. More than 88% of full-time, private sector workers in the United States receive paid time off . This benefit is ostensibly in place to improve