Don't be nervous, be excited! You've decided to make a change and are now going through the steps you need to go through to get there. This place seems to be an amazing source of support (have only been looking at it for the past couple of days since starting Exante) however I would recommend that you tell at least one person in the real world. There must be someone you know who will support you carrying through on your decision even if they don't agree with the decision itself - the only person I've told so far is my OH. He doesn't like the idea of it, but respects my decision and now that I've explained to him why it's for me he seems happy enough.
I must admit though, a small part of the reason I decided on Exante is because he recently gave up smoking for me and sometimes seems like he really regrets doing so. Therefore I've sold it as "I've given up something I love because you gave up something you love for me" but really it's just a way of me passive-aggressively guilt-tripping him if he dares fall off the wagon!
[Edit: And of course, it goes both ways - should /I/ fall off the wagon, I have no right to be criticising him for having a cigarette, plus it works as a positive mental reinforcement for me to remember that although I'm doing it mostly for me, I'm also doing it to support him. I can't expect him to stay clean off the fags if I can't manage to stick to this diet to achieve my goals.]