Unlike animals, human beings spend a lot of time on fantasies of the future. So, what could be done to turn these fantasies into strong goal pursuits? Fantasy Realization Theory has specified four kinds of self-regulative strategies of thinking about the future including mental contrasting, indulging, dwelling, and reverse contrasting. The present paper provides an overview of the concepts, the effects and the related research of mental contrasting. Mental contrasting is a self-regulatory strategy for goal setting, which specifies how people can turn their wishes into binding goals and plans, and eventually goal attainment. When people engage in mental contrasting, they first imagine a desired future outcome and then mentally elaborate on the present reality that stands in the way of attaining the desired future outcome. By imagining the future and thereafter imagining obstacles of reality, the future and the reality become simultaneously accessible, and the expectations of success are activated. The higher expectations of success, the more likely people commit to and strive for attaining the desired future out; in contrast, the lower expectations of success, the more likely people let go or disengage from goal pursuit. To explain the effects of mental contrasting on behavior change, research has identified three sets of mechanisms: cognitive changes, motivational changes, and responses to set-backs. Regarding cognitive mechanisms, research has shown that mental contrasting strengthens the association between future and reality, between obstacles in reality and the actions to be taken to overcome obstacles, and also changes individuals’ cognition of reality. Importantly, all these changes mediate the effects of mental contrasting on behavior changes. With respect to motivational changes, energization is considered a fundamental motivation variable linking mental contrasting and behavioral changes. Energization can be measured by subjective feelings as well as by objective measures like systolic blood pressure. This means when expectations are high, individuals feel more energized and systolic blood pressure increases, and when expectations are low, individuals feel less energized and blood pressure decreases. Importantly, changes in energization mediate the effects of mental contrasting on behavior change. In addition, the motivational changes may transfer efforts on one task to other tasks. A third mechanism underlying mental contrasting is that it may change the ways individuals react to negative feedback. Research has shown that mental contrasting promotes the processing of useful information embedded in negative feedback, which in turn helps individuals to form plans for implementing behavior changes. Mental contrasting also protects the self-view of competence against negative feedback and facilitates optimistic attributions for negative feedback. Research using MEG show that the process of mental contrasting is connected with brain areas related to intention formation, working memory, episodic memory, vividly imagining events and holding intentions as well as with action preparation. More recent studies have tried to combine mental contrasting with implementation intentions (MCII). Results of these studies indicate that the effects of MCII on goal pursuits are stronger than its two components by itself. Mental contrasting can be taught as a meta-cognitive, cost- and time-effective strategy to produce behavior changes ranging from interpersonal relationship, study and work to health domain. The effects of mental contrasting are cross-domain, cross-culture, cross-age and cross-time. Four recommendations for future researches are presented. First, future research should further explore the concept of mental contrasting and distinguish it from the other time-based concepts. Second, future research should examine the factors which have effects on the use and the results of mental contrasting. Third, research should be conducted in more specific fields. Fourth and finally, future research should consider how cultural background might influence the outcomes of mental contrasting.