Writing Project instructions is a distinct skill from writing a single prompt (Module 2's component structure), because Project instructions are persistent — they apply to every future conversation the Project will ever host, not just the one being drafted right now.
Good project instructions carry durable behavioral guidance: tone, format defaults, role framing, recurring constraints — generalized to hold across many future tasks, rather than specifics that only make sense for one particular request.
The common mistake: writing Project instructions as if they were a single, detailed prompt — over-specified to whatever task happened to be top of mind when the Project was set up. That over-specific instruction helps the first use case and adds noise (or actively conflicting guidance) to every other conversation the Project goes on to host.