One of the doctor who work in medical Plant told my friend that even he as a doctor. But he will never quit smoking due to this habit already 30 years with him.
Why? Is due to our cell. By sucking in the posion gas into our body. Body accumlate and it become a habit to cell. If this action being stop. The posion that left in the body with surface out through something like OSMOSIS. That is why those people who cut down too quit will face lot of problem whereby those 70 - 80+ old man still enjoy themselves in SMOKING.