Scott Belsky, in Making Ideas Happen: Overcoming the Obstacles Between Vision and Reality:

Ideas don’t happen because they are great — or by accident. The misconception that great ideas inevitably lead to success has prevailed for too long. Whether you have the perfect solution for an everyday problem or a bold new concept for a creative masterpiece, you must transform vision into reality.

Why even have a productivity system (such as GTD) at all? There are two reasons:

1. We need the ability to prioritize and sequence tasks
2. We need the ability to defer tasks without forgetting them

All of this flows from having more things to do than we can do immediately. Since you can’t do everything at once, you need an easy way to identify what is most important and sequence tasks in order of importance.

And, since you can’t do everything at once, you need an easy way to put things off to another day or time, without forgetting them altogether.