"Everybody knows smoking is harmful to your health." Here's the problem with what everyone knows. It's almost always wrong. It is almost a principle that if everybody, or almost everybody, believes something it is probably not true.
I don't mean things like obvious fact (there are planets and stars), or widely understood scientific principles (water freezes at zero degrees centigrade) or simple math (five time seven equals thirty five). I mean all those false generalities that people believe about life, nature, health, people, politics, societies, economics, and morality.
Smoking Is An Example
Smoking does not cause cancer. Nothing can be called a cause that is only a cause "sometimes." If smoking caused cancer everybody who smoked would have cancer. Almost everyone knows that is not true, but they still believe smoking causes cancer, and it's not even "might" cause cancer but a flat-out lying assertion, smoking causes cancer.
Here is a 112-year-old woman who has smoked 30 cigarettes a day for 95 years and she's still waiting for that cancer it's causing to kick in.
Many smokers live long healthy lives. Helmut Schmidt smoked three packs of cigarettes a day from his teens until they finally killed him at 96.
Jeanne Calment lived to be 122. Calment was often asked the secret to her good health. She would respond with a laugh and describe how she would frequently consume two pounds of chocolate a week, drank generous amounts of port wine and became a smoker at age 21. The smoking probably would have killed her if she hadn't quit when she was 117.
Those who live long do all the "wrong" things, like drinking, smoking, failing to exercise, and eating fried foods.
Everybody Is Different
Here is something true that almost no one believes, or at least consciously includes in their thinking: everybody is different.
Beyond the most fundamental biological aspects of human nature almost everything else about human beings is different for every individual. Yet one hears and reads every day recommendations by experts and so-called authorities on what everyone should eat, or not eat, what kind of exercise everyone should or should not do, and what is good or bad about almost every other aspect of human life for everybody; but almost nothing is true of everybody and in most cases not even most people. Every "official" pronouncement that begins, "everybody ought to...," or, "everybody must ...," or the more general, "people must ...," or the more insidious, "we must ...," is a lie, to which the only proper response is, "speak for yourself, buddy!"
What Should You Do?
Don't ask me? I'm not in the business of telling anyone what to do. I can tell you what I think the right principle is for deciding what to do. Principles aren't advice, they are descriptions of different aspects of the nature of reality.
For example, if one wants to be able to think and make choices, the more knowledge one has about as many things as possible the better they will be able to think and choose. Most people never learn more than they think they can get away with and thereby limit their capacity to think and choose which means they limit the scope of their whole life.
The principle is this. What one knows is all they can think about. One cannot think about what they do not know. What one knows is also all they have to think with. One cannot have any thoughts about something they know nothing about.
That's not advice or telling anyone what to do. No one has to learn any more than they choose to, but they cannot escape the consequences of ignorance.
The only advice I have for anyone is, "live your life they way you choose to live it." It's the only advice I ever give, and everyone I give it to always takes it.
One Final Principle
If you truly want to live your life free of wrong ideas, be sure you know why what you believe is true. Are they truly your own thoughts? The only way to be sure is to always think for yourself.