Firewall has an inbuilt Safe Mode, that will help you get in to your system if you accidentally lock yourself out of it, and you don't have easy access to the system console.
To activate Safe Mode, you need to reboot your system twice within 5 minutes, when Safe Mode is enabled. The Safe Mode setting is controlled by browsing to the 'Advanced' page, 'Advanced Settings' tab:
It is expected that this mode will be used when the machine is remote, or when it is difficult to access the console of the machine.
To activate it, reboot the machine a first time. Wait until the machine has fully completed its reboot, and then reboot it again. The firewall service will notice that the machine was only up for a short period of time on the last reboot, and if Safe Mode is available, it will temporarily delay applying the firewall rules for 5 minutes.
When Safe Mode is Active, you will have a large warning at the top of the page.
This will disappear when the machine has been up for more than 5 minutes, and the firewall has been activated.