Decide when your workday ends, or it never will on its own.

Work expands to fill whatever you hand it, and it will never announce a stopping point, because there is always one more message and one more thing to get ahead on. Without a line you picked in advance, the end of the day becomes whenever you run out of energy. That is not an ending, it is a collapse.

Choose a time and treat it as a real appointment. Close the laptop, change rooms, take a walk, anything that marks the switch. Some days you will break it, and the point is having something to break instead of drifting until bedtime.