had enough,
The real queston is "Why the mistakes?" and only you (assuming it is you we are discussing) know that answer.
Inattention? Confusion? Haste? Poorly learned lessons? Bad coordination? Inability to quickly digest the situation? Letting students get too far into the problem?
Search hard inside yourself, because the ability to see bad things coming, and catch them while the error is small, is the lifeblood of a pilot. Do not believe the pilot who says he makes no mistakes, he is lying. Believe instead that he finds the mistakes at an early stage, and corrects them in turn.