Let us all stop smoking

If I had the power, I would ban smoking altogether. Smokers must be happy that I don't have that power.
Everything in moderation is acceptable as a part of healthy lifestyle in a normal person, except smoking. because it does not provide any health benefit.
There is nothing guaranteed in life except the fact that we are all going to die one day. Even if we don't have any disease, still this is going to happen. The main underlying process is atherosclerosis (hardening of the arteries). This process is accelerated by smoking. In addition, smoking damages the lungs as well as other organs  leading to early death. Even the existence towards the end can be quite miserable. See why stop smoking for details.
For a heavy smoker, it is no good cutting down. It is like this - if a person smokes 40 per day, it is equivalent to jumping from a 40 storey building. If he cuts down to 20 per day, it is like jumping from a 20 storey building - the outcome is likely to be the same.
So, if possible, don't get into the habit at all. Let us all stop smoking.