This article presents self-validation theory (SVT) as a framework predicting when mental contents guide performance. First, we illustrate how confidence can validate people’s thoughts (goals, beliefs, identity) increasing and decreasing performance, depending on what thoughts are validated. This first section reviews examples of validation processes in guiding intellectual performance in academic settings, sport performance in athletes, as well as performance on diverse social tasks. SVT specifies moderating conditions for validation processes to operate. Therefore, in the second section of this review, we identify unique and testable moderators for metacognitive processes demonstrating when and for whom validation processes are more likely to occur. A third section calls for future research identifying new validating variables (e.g., preparation, courage) capable of increasing usage of unexplored thoughts relevant to performance (e.g., expectations). This final section examines new domains for validation (e.g., group performance, cheating in performance), discusses to what extent people can use self-validation strategies deliberatively to improve their performance and addresses when performance can be impaired by invalidation (e.g., due to identity threat).