If you make a mistake, ignore it and act as if nothing happened. After watching so many students perform the same techniques, examiners tend to get bored. They see what they expect to see. If you do not point out a mistake, they will probably not see it. Even if they notice it, if you act as if it never happened, they may doubt themselves and give you the benefit of the doubt. So, do not make any expression that draws attention to a mistake, such as a sigh, eye roll, flinch, or head drop. After a mistake, intensify everything you do. Even if the examiner noticed the mistake, make him or her forget it by giving a performance worthy of spectator applause..
You have some slack
Each organization has minimum requirements for advancement to the next belt level. Examiners are trained to look for completion of these minimums, such as correct movements in patterns or correct technique in step-sparring. At the color belt levels, examiners give students a lot of slack. Regrettably, at the lower color belt levels, students who fail to advance will probably quit training. If a student performs the steps of a pattern correctly, he or she will probably pass even if their technique was sloppy. If the board breaks, he or she will probably pass even though the technique was technically poor. Some organizations award temporary or recommended belts in addition to the standard belt levels. This awards a borderline student the belt, but the student's instructor must certify the student as a standard belt before the student may test for the next belt. You have some slack, but examiners will not lower organization standards just to promote students.