Feierabend is the end of the working day. Duden also records the word in a wider sense. Für mich ist Feierabend means that the speaker cannot or will not go on, and that for him the matter is over. Damit ist bei mir Feierabend means that a matter is closed and done. In everyday speech, Jetzt ist aber Feierabend! means that is enough now. A phrase from mining says the same thing. Schicht im Schacht, literally shift in the shaft, means that something has come to an end.