Too much certainty creates inflexibility

One of the ten reasons you don't have succes: Too much certainty creates inflexibility. If you’re sure that your plan is correct, and refuse to accept the possibility of error, you may well find yourself stuck when an unexpected change comes about, or when your plan takes you in an unexpected direction. However strong your plan and however sure you are of your goals, make room for periodic reassessment. (Source: Lifehack.org)