TEARS AND SMILES ARE PARTS OF LIFE这句话有错误吗

TEARS AND SMILES ARE PARTS OF LIFE这句话有错误吗
TEARS AND SMILES ARE PARTS OF LIFE
PART可数吗?
还有这句谚语A good medicine tastes bitter.良药苦口,忠言逆耳
MEDICINE 不是不可数吗?