Many theories argue that goal striving is more intense when people have optimistic expectancies for achieving the goal and when attention is self-focused. Brehm's motivational intensity theory, however, predicts that the intensity of motivation is only as high as necessary, so people will try harder for difficult tasks than for easy tasks, all else equal. The present experiment compared these two approaches by manipulating two levels of selffocused attention (low and high self-awareness, via a mirror) and two levels of task difficulty (easy and difficult). Effort was assessed as cardiovascular reactivity, particularly change in systolic blood pressure. Neither high selffocus nor an easy task per se caused increased effort; instead, high self-focus significantly increased systolic reactivity when the task was difficult. Effort was thus higher despite less optimistic goal expectancies, a finding that is predicted by Brehm's motivational intensity theory but not by traditional self-regulation models.