Mentally contrasting a desired future with reality is a self-regulation strategy that helps people effectively pursue important personal wishes. People with higher self-regulation skills are more likely to spontaneously use mental contrasting. Because one central cognitive function underlying self-regulation is working memory capacity, we investigated whether people with low rather than high working memory capacity are less likely to spontaneously use mental contrasting. Study 1 provided correlational evidence that participants with lower working memory capacity, as measured by the Operation-Span Task, were less likely to use mental contrasting when elaborating an important interpersonal wish. Study 2 provided experimental evidence that manipulating low working memory capacity by inducing cognitive load (vs. no load) led fewer participants to use mental contrasting. The findings have theoretical implications by illuminating the processes that impede mental contrasting, and they have applied implications for understanding how to foster the use of mental contrasting in everyday life.