I know very well you have steady nerves but what is strong can turn weak as well.

steady 的意思是"稳定的、稳固的"，形容事物保持平衡或不变的状态。nerves 指"神经"，这里比喻人的心理状态或承受能力。 steady nerves 指"稳定的神经状态"，比喻一个人能够保持冷静、不易受外界影响的心理素质。