How to say it in English before meeting?

［said when making an appointment］ (let's) not leave without seeing each other/Be There or Be Square

Be there or be square was the last thing Americans said on a date a long time ago. Squre can be understood as packing and leaving. Of course, this is a joke. "You can either go to the appointment or pack up and leave." Translated into Chinese, of course, it is "be there or be square."

This is very outdated English. Now people will say "Don't miss it".