I was going to mention caffeine. Active smokers metabolize caffeine at almost twice the rate of non-smokers. That usually means you drink more caffeine and if so, after reducing smoke, you would experience greater anxiety and agitation from the caffeine intake.
Here is a website that gives some tips on breathing, contacts etc.,
Quit smoking -- the classic boilerplate points
In addition, monitor your mood as tobacco smoke (not nicotine) has an antidepressant effect, influencing MAO in your brain. We know this antidepressant effect exists but don't understand the mechanism.