(Suppose your friend has become a smoker. You know smoking is a bad habit. It causes many dangerous diseases. Now write a letter to him describing the bad effects of smoking.)
Date: 00 Month: …. Year: 0000
Dear XYZ (Name),
It is a long since I heard from you. Your silence pains me much. It will be a pleasure for me if you write to me time to time. It shocked me greatly when I learnt that you have become a chain smoker. You are quite sensible and learned. So, I think you could realize the harmful effect of smoking. It damages our lungs day by day and man loses his longevity. Every 15 cigarettes you smoke will cause a mutation in your body, mutations are how cancers start. It causes many fatal diseases like cancer, heart attack, bronchitis, etc. It also harms the nerves, damages the brain and sometimes spoils the character. In fact, smoking increases your risk of having a stroke by at least 50%, which can cause brain damage and death. And, by smoking, you double your risk of dying from a stroke.
In another sense, it can be said that smoking is as bad as committing suicide. Please do not do any injustice to yourself. The good news is that within two years of stopping smoking, your risk of stroke is reduced to half that of a smoker and within five years it will be the same as a non-smoker. I shall be highly glad if you give up this bad habit without delay.