You can't control everything

 ... and let go where you can’t.

When you focus on the things you can’t control, the pressure—and your anxiety—are intensified. Focus on the things you can control and let the rest take care of itself.

Ignore the rest. We worry about things that we have no control over. But worrying never fixed anything. 

The stoics are saying that if you focus your energy on what you can change, you’re going to be a lot more productive and effective. 

Focus on what you can control. Solve the problems that you can and tackle what is in your influence, but accept the things that are out of your control and that you cannot solve. Let them go.