your anxiety is what is talking now - and it is what is causing you to perform below your usual level of competence. if you were not competent for this job they would have let you go already. try to find ways of calming yourself before starting work and whenever you can take a moment while there. arriving a little early will help so you are not rushed. regulate your breathing, close your eyes for a moment and visualize a peaceful scene, tell yourself that you are safe and in control, etc. whatever works for you. you can do this, man!
As my life goes on I believe somehow something's changed
Something deep inside...
I've been searchin so long to find an answer
Now I know my life has meaning
Now I see myself as I am, feeling very free...
When my tears have come to an end I will understand
What I left behind: a part of me. Chicago