One of the points David Allen makes in his book that I didn't 'get' first time round was : "It's important to get reminders of everything big and small recorded in a system outside your head not because everything is equally important but because everything isn't."
And it has to be a system that you trust or you won't be able to let go of those mental reminders. Trust means not just that it won't get lost but that you know that you'll review it regularly enough to deal with the items.
