I agree with Rainbow - reiki brings issues to the light that were there before - so we can heal them and move on. I remember feeling angry after my second attunement for about a week - which were issues from my childhood I had not resolved. Sending reiki to myself as a child cleared it up. But if you do not know the source of anxiety, you might want to try emotional freedom Techniques - known as EFT. Very simple tapping could very well free you from your anxiety in 10 mins or less.
All the information is available on the web for free just search "EFT".
Peace
Sky