lěng nuǎn zì zhī
see 如人飲水,冷暖自知|如人饮水,冷暖自知[ru2 ren2 yin3 shui3 , leng3 nuan3 zi4 zhi1]
rú rén yǐn shuǐ , lěng nuǎn zì zhī
the person who drinks it knows best whether the water is hot or cold (Zen proverb); self-awareness comes from within
to know best by personal experience