Although you might be passionate about what you do, you don't need to be stressed to do it well. In fact, you may actually perform your best when you're the most relaxed.
Actor Bill Murray said in an interview at TIFF:
You have to remind yourself that you can do the very best you can when you're very, very relaxed, no matter what it is, whatever your job is. The more relaxed you are, the better you are. That's sort of why I got into acting. I realised the more fun I had, the better I did. I thought, well, that's a job I could be proud of.
Most people relax when they have finished their work, but relaxing before or even during the process has benefits as well. This could mean prioritizing exercises or activities that help you relax. Certain music could also relax you. However you do it, it's good to remember that stress isn't always the thing that drives us to do our best.
Bill Murray Day @ TIFF [YouTube]