There are NO good effects of smoking because it is bad for your health but there are some things that people who smoke like about smoking.
For most people, their first cigarette is pretty difficult because it tastes horrible and makes them cough. All that coughing and spluttering is not relaxing, it's not what makes you go back for more. You smoke more because you get hooked on the nicotine or because you want to.
When you are hooked, if you don't have a cigarette, then you get withdrawal symptoms and that is what stresses you out.
We were supposed to be telling you about the good effects. We cannot think of any. Maybe for some it is a social thing, but if you smoke because you feel the pressure, you might not be doing what you want to.
We give up. Let us know if you think there are good reasons to smoke.