One possible explanation is that idealized thinking can sap motivation, as outlined in a study published earlier this year in the Journal of Experimental Social Psychology. Researchers asked college student volunteers to think through a fantasy version of an experience (looking attractive in a pair of high-heeled shoes, winning an essay contest, or getting an A on a test) and then evaluated the fantasy’s effect on the subjects and on how things unfolded in reality. When participants envisioned the most positive outcome, their energy levels, as measured by blood pressure, dropped, and they reported having a worse experience with the actual event than those who had conjured more realistic or even negative visions.