Congratulations! I quit ten months ago with the help of http://www.quitnet.com/
it's been so awesome! I started smoking when I was 13 and quit when I was 41. I'd only quit one other time before and only for four months. I don't count my pregnancies, because something about my hormones and changes in my body chemistry made cigarettes taste and feel nasty.
The funny thing was that all those years, I kept saying I couldn't quit because I was going through some crisis or another and I just couldn't handle one more major bit of stress. About two or three days into my quit, I threw my back out and literally couldn't get out of bed for a week. My car was undriveable, but it only needed about $100 worth of work and my family started tearing me apart emotionally when I asked if there was any way I could borrow a few bucks under the circumstances.
The only thing I could feel good about myself for was my quit.
It took a lot more rehab to get my back working again than it ever had before, but after improving my diet and starting some very basic exercise (first walking a few blocks every day no matter how much it hurt, now riding a bicycle across town twice a day) I feel fifteen years younger than I did when I smoked.
At four days, the drug is out of your system but it's normal to still have cravings and temptations and to be an ex-smoker first and foremost. It's an exciting and wonderful thing to be! I'm so happy for you!