Human beings are cognitive misers. One facet of this effort avoidance is the reluctance to voluntarily switch tasks when repeating the same task is allowed. Yet participants sometimes voluntarily switch despite the resulting costs. This paradox might be resolved if the individual switching ability or sensitivity is taken into account. Hence, we investigated whether the voluntary switch rate (VSR) is governed by the objective or the subjective (introspective) switch costs. Three experiments (N1=120, N2=100, N3=100) were conducted utilizing voluntary task switching with forced and free task choices intermixed. In Experiments 1 and 3, objective switch costs were measured on forced tasks, and subjective switch costs were calculated from (introspectively) estimated reaction times in a separate phase. In Experiment 2, objective and subjective costs were measured in the same phase. In Experiments 2 and 3, we additionally manipulated the forced switch rate (FSR). Results show that objective switch costs were lower in blocks with higher FSRs and that this subtle modulation was captured by the subjective estimations. Moreover, the objective switch costs predicted the VSR in Experiments 1 and (partially) 3: Participants with higher switch costs switched tasks less often voluntarily. The subjective switch costs predicted the VSR only in Experiment 3 (the lower the subjective costs, the higher the VSR). Hence, the present study offers first insights under which circumstances introspection guides decision-making during voluntary task-switching.