The boss leaving early is when you find out if you work there or just perform there.

The hour after the person in charge leaves is the most honest hour of the day. Everything you do in it is unpaid in the sense that nobody is recording it, so whatever is left is your actual relationship with the work. Coasting then is not laziness exactly, it is a signal that the job is a performance you put on for an audience. That gets noticed eventually, usually through results rather than through anyone catching you.

Pick one thing to finish properly in that window today. Not to be seen doing it, just to know.