I'm on my third week, and I'm pretty enthusiastic. It seems really easy, looking back on it, but the first couple of days did have that feeling of forgetting to do something, or that you've misplaced something. I also had an issue of not knowing what to do with myself, where I would usually go outside and smoke a cigarette, now I could just stay put. But then that feeling of misplacement comes in.
There's also the self-image thing: I thought of smoking as somehow a part of my "thing", the image I present to the world. A visual aspect of my personality manifested in a physical trait. I'm a smoker, right, so I need to smoke.
All of that passed. It is a little like getting married. You're crossing this threshold in your mind, the world does not shake in response bit it seems like it should. Yesterday, I WAS a smoker. Tomorrow, suddenly, I'm not? That seems scary. It seems like an upheaval, or some fundamental parting of ways with "the old you". Then you wake up and realize that you're the same person, everything important is just like it used to be. That's the mental shift, when you choose to cross that threshold and drop that label, then it all gets easier. There IS a physical element to it, but really, it is mostly mental.
Good luck, and stay strong. It is worth it!