伤口不深不知疼感情不毁不知冷
[shāng kŏu bù shēn bù zhī téng găn qíng bù huĭ bù zhī lĕng]
Translating to 'One doesn't know the ache unless wounded, and won't understand coldness until feelings are betrayed'. Implies wisdom drawn from hardship: only painful experiences let a person really understand true suffering and the value of emotions, which is hard-earned understanding and maturity.