CC:

Being a little nervous is okay. It helps you to stay alert, and it's simply Nature's way of reminding you that you may not have enough experience at this (yet) to feel fully confident. Ride where you feel comfortable, and as you gain confidence (and skill!) you can work your way up to more complex situations. I know it sounds a lot like a cliche, but a lot really is "getting used to it."

A good video that I use in nearly all my adult classes is one called "A Cyclist's Eye View," distributed by the League of American Bicyclists. It's available on YouTube:

ABC Quick Check:
http://www.youtube.com/watch?v=9VziOIkNXsE

A Cyclist’s Eye View:
Part 1. -- http://www.youtube.com/watch?v=ZFjCza5e1kw
Part 2. -- http://www.youtube.com/watch?v=XIr3mI96FZk
Part 3. -- http://www.youtube.com/watch?v=vLu0DHPeYm8

You might also want to check out one of the League's Traffic Skills classes, and see if one is available in your community. These include not just lectures on traffic rules, road hazards, and how to fix flats, but also several hours of supervised, coached riding in the typical traffic in your community.

Tom