When I discuss the concept Mind Like Water, I feel like I am teaching a buddhist concept. In GTD, mind like water is the state when all of your responsibilities and tasks are managed and you can focus on what is in front of you, or nothing at all. This opens up your headspace for your most productive and creative thoughts. This only happens if you have a system to manage your tasks and responsibilities in a way that you trust and ensures that you keep the promises you make.
How do you achieve it? In GTD, you write down every task and responsibility you have, you review regularly to ensure that nothing is missed, and you complete tasks in the contexts that they make the most sense to do. It’s that easy (easy?).