The current study examined the effects of good and poor control and changes in blood glucose following self-control depletion on task persistence. Good self-control attenuated the effect of depletion on task persistence. Poor control exerted a main effect; however, there were no significant interactions between poor control and self-control depletion. In addition, the association between depletion and task persistence was partially mediated by decreases in blood glucose. Task persistence in the experimental, but not control, condition was correlated with several risk behaviors. These correlations provide support for the external validity of the laboratory experiment. The differential effects of good and poor control support a two-mode model of self-control. The interaction between the depletion manipulation and good self-control suggests that associations between good self-control and behavior may be due, in part, to good self-control reducing the effects of self-control demands on behavior.