Goal of the investigation is to determine, whether the state of ego depletion alters decision making. Due to past research, we expect participants who have had a mentally demanding day, to be less likely to choose an effortful subsequent activity. In contrast to previous investigations, this study makes use of the subjects’ real life in order to examine the impact of ego depletion. Ego depletion is therefore not experimentally induced. Research also suggests that participants who report having dealt with a lot of self-control attempts will be less likely to choose an effortful subsequent activity. Similarly, it is expected that participants who report having been externally motivated to be less likely to choose a subsequent effortful activity. Furthermore, this pre-registered study seeks to evaluate the implications of the strength-model (Baumeister, Vohs & Tice, 2007) and the process-model (Inzlicht & Schmeichel, 2012). Both models postulate that the exercise of self-control negatively affects subsequent self-control attempts, but the models are based on different explanations: whereas the strength model assumes that a limited self-control resource is the reason for the drop in self-control performance, the process model assumes that a change in motivation and attention is the reason for the drop in performance. Therefore, this study wants to test the hypothesis that self-control attempts moderate the effects of mental demand on decision making (thus supporting the strength-model). The hypothesis that how participants are motivated (internally vs. externally) moderates the effects of mental demand on decision making (thus supporting the process model) will also be tested.