Mental contrasting of a desired future with the present reality strengthens goal pursuit when expectations of success are high, and weakens goal pursuit when expectations of success are low. We hypothesized that mental contrasting effects on selective goal pursuit are mediated by a change in the meaning of the present reality as an obstacle towards reaching the desired future. Using explicit evaluation of reality (Study 1), implicit categorization of reality as obstacle (Study 2), and detection of obstacle (Study 3) as indicators, we found that mental contrasting (versus relevant control groups) fostered the meaning of reality as obstacle when expectations of success were high, but weakened it when expectations of success were low. Importantly, the meaning of reality as obstacle mediated mental contrasting effects on goal pursuit (Studies 1, 2). The findings suggest that mental contrasting produces selective goal pursuit by changing the meaning of a person's reality.