To leave the castle is to step out of your comfort zone.
And what that means, to be in a space of discomfort, varies with time, situation and by person.
The emphasis is on being in the discomfort, on facing what causes you to flinch, procrastinate, defend or run.
What interrupts your flow can be the big things down to small, everyday stuff.
leave the castle is what I tell myself to get moving toward, rather than away.