Smoking damages the health of many people who are smokers, even causing premature death. Even if you have a great-aunt who lived to a hundred and thirty while smoking 50 cigarettes a day and washing down hamburgers and chips each day with a bottle of whisky, you have no way of knowing that you will have her happy outcome. Smoking damages the health of other people - in particular the vulnerable babies and children. Smoking costs significant resources in hard currency. A smoker is an example for others to follow and hence a smoker leads others into a death-trap.
Smoking is evidence of addiction and therefore a lack of self-control.
Paying for cigarettes supports an evil industry with money God has given you. This hardly needs much comment. Clearly smokers are contributing wilfully to their own death and the death of others. I really like the way the Westminster Divines discussed the Ten Commandments. They were pretty comprehensive.