I have always wondered about this too. I agree that it can be related to anxiety because the unknown doesn't feel good when you are anxious, so definite answers are more comforting. I have actually reached the gray without even working on this specific problem but I did work on the anxiety. So decreasing my anxiety might have fixed this issue?? The last thing that I have worked on was my attachment which really improved things for me.

I would work on each black/white issue as it comes up. If you can see the gray in each issue the practice might get you somewhere?