guideline: any guide or indication of a future course of action.
Harmless enough, right? Guidelines are offered to us for many situations. I use the word myself all the time teaching guitar; it's a gentler and less restrictive word than "rule".
Still, lines are lines and lines can suggest shapes. Even that innocent definition above mentions a "future course of action". And when I'm trying to create - a process that thrives on unconscious thought - lines that can point me toward already existing shapes or direct me toward a future course of action have the potential to prevent me from seeing a new shape or, a different future.
Lately, I've been paying more attention to barriers, linguistic or otherwise, that may circumscribe my creativity. Aren't the ropes and buoys used to indicate swimming areas a guideline of sorts? I'm all for that kind of box to keep children safe while they're swimming. I just don't want to allow guidelines to create a box that could restrict my creativity. There's a fine line between that kind of box and a cage.