When I tried to give up some years ago I found I was wearing a patch on each arm, chewing gum and still smoking 40 untipped a day ~ I felt no different but my work colleagues said I was rather "loud" and would I mind not chewing all day. One concerned director, noticing the patch on my arm asked if I had had an injection.
I figured it wasn't worth the effort.
Some years later when I was told No Heart Op unless you stop smoking I stopped immediately and never looked back. The sod of it was the heart bypass failed to "take". I have stayed off the fags but still miss 'em.