Although people expect to improve by investing effort in solving a problem, several studies have found negative time-confidence correlations in problem-solving tasks. The present study employed the metacognitive approach to illuminate why, despite lengthy thinking, people provide solutions with low confidence. According to the proposed Diminishing Criterion Model (DCM), as people invest longer, their confidence in their solution increases in a goal-driven manner, in accordance with the common belief. Nevertheless, the process ends up with a negative time-confidence correlation, because people find lower confidence levels as satisfactory as they invest longer in a problem, reflecting a compromise in their stopping criterion. The hypotheses derived from the DCM were supported with two problem types. When a “don’t know” response was allowed, the participants still provided low confidence solutions after lengthy thinking, suggesting that they found these low confidence solutions to be satisfactory. The study offers reconciliation between beliefs and empirical findings.