The present dissertation investigates the interrelationship between personal choice, affective influences, and the psychophysiology of cognitive effort. Systematic affective influences on effort intensity have been reported throughout the past decades: positive and negative affective states systematically influence striving in terms of effort intensity (Gendolla, 2000). However, an independent research line makes equivocal assumptions about the role of affect in action execution: theorizing and research on volition suggests that goal pursuit should be shielded against incidental affective influences because deliberating and choosing actions and goals oneself leads to a mindset that protects goal pursuit from conflicting temptations and unintended affective influences (Gollwitzer, 1990, 1993; Heckhausen & Gollwitzer, 1987). The aim of the present dissertation was therefore to integrate these two theoretical approaches and research lines by investigating under which circumstances affective influences on effort occur, by considering the crucial role of personal choice. Across five empirical studies, we show that affective influences on self-chosen actions are weaker than on externally assigned actions, because personal choice leads to higher commitment and task focus, resulting in stronger shielding against affective influences during action execution in order to facilitate goal attainment. Thus, the present studies suggest that the impact of affective influences on effort depends on how the individual engages in action – by personal choice or external assignment.