百毒不侵就怕她入你心
[băi dú bù qīn jiù pà tā rù nĭ xīn]
It means 'immune to all poisons, but still vulnerable to falling in love with her'. It implies that someone might be tough or indifferent, but when they encounter a special person, their defenses fall. The expression conveys the idea that love can overcome one's usual resilience.