Ann,
My work is quite demanding and although I never really had to deal with "lack of focus" due to not smoking I have had to deal with it! It can be so aggravating! I usually try to go outside myself for less than 30 seconds and then get right back to work. I'm a CNA and becoming a RN so if that doesn't work I'll step away from the patient--usually he/she is part of my problem--out of their room if possible, go to the washroom, do some paperwork, or anything that will keep me from getting too lost in the "brain fog."
I don't know if that makes any real sense or helps at all, but sometimes I don't use the best words to explain myself! Best of luck with your quit! You've taken the first step, just take the next and you'll be in the right direction for your life and the lives of those you care about!!!
Lauren