Most of us have experienced moments when we could not recall some piece of information, but felt that it was just out of reach. Research in metamemory has established that such judgments are often accurate; but what adaptive purpose do they serve? Here, we present an optimal model of how metacognitive monitoring (feeling of knowing) could dynamically inform metacognitive control of memory (the direction of retrieval efforts). In two experiments, we find that, consistent with the optimal model, people report having a stronger memory for targets they are likely to recall, and direct their search efforts accordingly, cutting off search when it is unlikely to succeed and prioritizing search for stronger memories. Our results suggest that metamemory is indeed adaptive, and motivate the development of process-level theories that account for the dynamic interplay between monitoring and control.