Remember that anxiety that you have, is only an illusion. It is not reality. Anxiety is good, adrenalin is good in order to improve performance - just look at sports stars!
You can only live life forward, looking back afterwards and reviewing it is about learning, its about understanding.
If anxiety is about an illusion than create a postive look - see people smiling and clapping at a presentation that you are about to give. See a succesful conclusion with the task no matter what that looks like....
Make the illusion work for you, not against you. You don't know how it will be, so why worry about a negative outcome? Picture a success, picture a celebration, let the illusion work for you and that will control the anxiety.