Possum up

A phrase that can be used two different ways. You can use it to tell some to be laid back about something. Or it can be a way of saying hunker down and get it done.

Mom: You're not supposed to be playing video games on school nights.
son: come on mom just possum up.
Example 2.
guy 1: I have a lot of work to do tonight.
guy 2: I guess you'll just have to possum up and get it done.