Research on goal attainment has demonstrated that people are more likely to reach their goals when they form implementation intentions. Three experiments tested whether implementation intentions lead to tenacious goal striving following blockage of an initial attempt to reach the goal. In all three experiments some participants were instructed to form an implementation intention and other participants were not. Subsequently, the initial goal-directed attempt of all participants was unexpectedly blocked. Experiment I found that implementation intentions resulted in more attempts to realize one's goal. Experiment 2 showed that when participants formed an implementation intention their repeated attempt was acted out as intensely as their first, blocked attempt. Experiment 3 found that implementation intentions still allow people to seize an alternative, more onerous means to realize their intention. These results imply that implementation intention conserve self-regulatory strength. After goal blockage, the remaining strength can be used to continue goal-directed action.