He ,my friend ,was frustrated by his poverty.
他,我的朋友,因为贫困而感到灰心丧气.
短语 be frustrated by 因为...感到气馁/灰心丧气
frustrated 本身就是一个形容词 灰心的
你也可以把它看成被动句 动词frustrate 加了ed 表被动