百毒不侵其实已麻木至极
[băi dú bù qīn qí shí yĭ má mù zhì jí]
It means literally 'Impervious to all poisons because I've grown numb.' One could infer from this that although seemingly nothing can hurt the individual anymore, inside they’ve become so accustomed or indifferent towards negative events due to continuous emotional injuries.