Go off the rails
By Pamela, May 10 2020If someone loses complete control of their behavior or emotions, then you can say that they have gone off the rails. We use the expression go off the rails to refer to someone who has started to behave in a strange or abnormal way. In many cases, their actions are considered to be inappropriate or unacceptable compared to their usual standards. As a result, they are likely to cause damage either to themselves or others.