I've also been wondering whether GTD has given me a mind like a martial arts expert
constantly looking around to check whether there are any dangers, rather than a mind
like water. Some people said that having everything captured feels very different from having almost everything captured, and that touched off a perfectionistic or competitive streak in me.

Things I do to reduce anxiety include: using the book "Feeling Good: The New Mood Therapy" by David Burns; taking a calcium supplement; doing a ritual which is essentially
a declaration of rejection of perfectionism and an acceptance of good, imperfect
actions; affirmations.

You could do something like this: imagine that you could visit a professional who
would help you overcome your anxiety and get to the proper mind-like-water state.
Then take the amount of time and money you would have spent on this
professional and set it aside. Then, for the rest of the year, tell yourself that
you can relax, because if you miss an appointment or something you can use
the saved-up time and money to compensate. Also tell yourself that the amount
of time you spend in a relaxed state will probably far exceed in value the
time lost due to missed appointments. In other words: try to relax and not worry, to such an extent that you miss at least one appointment this year. There will be
a small number of particularly important appointments such as job interviews
that you won't include in the plan. This is just an idea I thought up.

You can set aside times when you're trying to think up things to add to your
system, and other times when you're engaging in a relaxing activity and
don't expect to think up any action items during that time.