The will is there, but not the strength (idiom, from Confucian Analects). / I really want to do it, but don't have the resources. / The spirit is willing but the flesh is weak.
lit. the falling flowers are yearning for love, but the heartless brook ripples on (idiom) / fig. one side is willing, yet the other one remains indifferent (usually of unrequited love)
神女有心,襄王无梦
shén nu:3 yǒu xīn , Xiāng Wáng wú mèng
lit. the fairy is willing, but King Xiang doesn't dream (idiom) / (said of a woman's unrequited love)
死士
sǐ shì
person willing to sacrifice his life (for a good cause)
人球
rén qiú
person who is passed back and forth, with nobody willing to look after them (e.g. a child of divorced parents) / (esp.) patient who gets shuttled from hospital to hospital, each of which refuses to admit the patient for treatment