The failure was a sobering experience that made him face reality.

sobering 是形容词，由动词 sober（使清醒、使冷静）加上后缀 -ing 构成。sober 本意是"清醒的、未醉的"，引申为"冷静的、严肃的"。 sobering 表示"使人清醒的、发人深省的"，强调某种经历或事实能让人从幻想或错觉中清醒过来，更清楚地认识现实。