SOS bombs going off

So here's my story.I ,stop smoking nowquit smoking on March 13th of 2009. I purchased a new car 3 weeks later so the smell of smoke was non existent. Since then I caved in on my birthday a month later when I was hanging out with 20 or so people who smoke. After that I said I'm staying away from them and sticking with this. Well about 2 weeks ago I was out having drinks with a client who smokes. We were at a bar with someone else who also smokes who is competing with me for the clients business.I couldn't stand seeing the two of them bonding over cigarrettes together alone talking about work. I caved in and had a cigarette with them to help close the deal. I'm trying to justify why this is a good idea because it will make me a lot of money.If this was the case I would be ok with the way things workout,smoking cessation, but since then I have found myself smoking. I've smoked about a pack of cigs since December 9th. What do I do? How do I combat this?The only other time I've slipped was about 2 months ago when I was at a gas station. I went to the counter and said fillup on number 6 and a pack of marlboros. I didn't even think about it. I was driving home and smoking a cig. When I realized what I was doing I threw the pack out the window. I'm fighting like crazy again to get back on track.