How to stop fatal error when loading theme template file directly

I define some variables used in my theme at the top of functions.php….one of them being

$press_here="yes";

Then at the top of my template files I use

<?php
global $press_here;
if( !isset( $press_here ) )
    die('You don\'t have permission to view this page.');

Which then gives the error message I define there when being accessed directly, nothing more.
(Thanks @t31os )