On his first day at work he was nervous and walked on eggshells.
Tips
usage
Always doubled. 兢兢业业 ('diligent and conscientious') is a compliment; 战战兢兢 ('trembling with fear, treading carefully') describes anxious caution. Both come from the Classic of Poetry.
The left 克 is one of a doubled pair; the old form pictured a person bowed under a heavy weight on the head, which gave the sense of careful, anxious self-restraint.
The right 克 repeats the figure. Doubling it intensifies the meaning to trembling caution; the 儿 ('legs') element at the foot of each is the indexing radical.
Filed under radical 儿 (ér) by convention. 儿 is not a separate component in 兢, so no strokes are highlighted.