Performance anxiety

I have another 22 hours or so until I start working on my novel again but I'm already feeling nervous about it. I'm pretty sure this comes from feeling inadequate - wondering whether I'll be able to write tomorrow and do a good job - which annoys me because I've been writing for three months now and I should be feeling more comfortable and confident about what I'm doing. After all I've been preparing for this my whole life so maybe I should give myself a break and have a little more belief in my abilities.

But perhaps the day I start feeling complacent is the day quality suffers. I should set myself high standards and expect only the very best; otherwise I might as well go back to writing as a hobby. Because if I don't produce the best novel that I have in me, how can I expect a publisher or an agent to pick it up?

I guess the trick is to never take writing for granted but not to let the performance anxiety stop me from getting the job done. Some days it's a very fine line.