百毒不侵的人都曾无药可救
[băi dú bù qīn de rén dōu céng wú yào kĕ jiù]
'Those Invulnerable to Poisons Have Once Been Hopelessly Afflicted' expresses resilience, implying that the current toughness or nonchalance has come through overcoming many adversities and hardships previously considered insurmountable.