go/fall to pieces idiom
C2 （在精神方面）崩溃，垮掉;十分激动，极度紧张
If someone goes/falls to pieces, that person becomes unable to think clearly and control their emotions because of something unpleasant or difficult that they have experienced.
She just went (all) to pieces during finals. 她考试时脑子里一团糟。
（机构或系统）四分五裂，瓦解
If a relationship, organization, or system goes/falls to pieces, it fails.
Their marriage began to fall to pieces after only a few months. 才过了几个月，他们的婚姻就开始走下坡路了。