Hesitation is the biggest trap that can undo you in pivotal career moments, according to the author. When a pivotal career moment arises, hesitation allows doubts and fears to take over. Instead, the author advocates for taking immediate action when these moments occur. By acting instead of waiting to see what happens, you access qualities like confidence and resourcefulness that were there all along. The key message is that in pivotal career moments, the choice is yours - you can either hesitate or choose to act and define success on your own terms.