Brent's question is the answer. It's not a problem. GTD is designed to get a mind like water. You will get most, but not every single thing, out of your head. For example, you will have a list of NAs which you prioritise in the moment from resources available, energy levels and intuition. In other words, your brain still does some stuff.
With NA and tickler items I trust that on the day I'll know. The item is out of my head until that time and then I think about it. If you have so many that you can't distinguish then look carefully if they should be there - what items can be on a someday maybe and be picked up during a weekly review, or set a simple way of coding them. "T:do this" to denote a tickler entry perhaps. Personally I wouldn't do that because it creates one more thing to manage.
As always, an objective viewpoint makes what seems like a problem not a problem at all.
Thanks very much.
Glad to help.
David/quantumgardener: That's an excellent distillation of the Next Actions list, far better than anything I've ever managed.