昨日阳光晒不干今日衣裳
[zuó rì yáng guāng shài bù gān jīn rì yī shang]
Means yesterday's sunshine can not dry today's clothes. It implies even when past positive experiences (like sunlight drying your clothes metaphorically), it cannot replace or overcome negative current experiences (clothes wetted by bad experiences). So it expresses certain nostalgia towards the past but emphasizes current difficulties or problems unsolved or untainted by the good memories.