The research within this thesis focused on examining the concept of self-control; the ability of regulating and/or controlling responses, e.g. choosing a fruit salad rather than a more tempting chocolate cake. Self-control was of interest as evidence has repeatedly observed that the ability to apply self-control continually over time poses difficulty. Namely, when faced with completing two sequential tasks that both require self-control, typically prior research reported that the first task is completed successfully but there is a temporary impairment in self-control performance in the second. The work in this thesis attempted to address why a temporary deterioration in self-control performance occurs. Specifically, we drew on the strength model, which posits that self-control is directly fuelled by a limited resource that gets depleted when initially applied, leaving limited resources available for the second task. Glucose was proposed – though with recent debate - as the physiological resource and consequently we assessed the role of glucose in sequential self-control task performance. In addition evidence suggested that rather than self-control deterioration stemming from resource depletion, it is connected to a reluctance to allocate resources based on a lowering in intrinsic motivation. The seven studies that were conducted attempted to further examine and add to the debate about the factors that play a role in self-control depletion following prior exertion, with a specific focus on the effects of glucose and intrinsic motivation. Overall the findings from the studies somewhat challenge the direct role of glucose: no relationship between glucose and sequential self-control performance was observed. Intrinsic motivation was however predicted to be a stronger predictor of self-control ability over time, suggesting that perhaps the temporary deterioration in self-control performance is one of resource allocation rather than depletion. More research is needed to corroborate these findings but the accumulation of evidence within this thesis - added to the current research - supports more of the recent literature i.e. motivation plays an important role in successful self-control exertion.