Most people think life is a bed of roses, is all about sunshine, enjoyment etc not knowing that there's always a tough time and the ability of one to overcome this time makes him great. Tough time is the point through which poor and successful people emerges depending on the choices and decision they take.
Most traders and investors are inpatient they only think of the positive side of it ( making profit) not knowing there will always be a loss someday, well most of them know but when they make losses they became frustrated and unstable, some will give up because of that little experience. Sometimes we make losses and we have bad experience like we offend God but no, we are only been tested. Some of the spirit of a trader or invest is "I can make it mindset, resilience...
I read through what you feel that everyone has to know about trading. Your post is in line and understandable. But with respect to your post title, I feel that what you need to know about trading is that TRADING IS NOT FOR EVERYONE.
YES, you read it clear. If you lose and keep losing, quit trading and find some other things to do. Trading is more than profits and losses, it takes patience and emotion to survive in the trading market. If you have tried trading for sometimes and no matter how careful you applied your strategy, you still don't succeed. Please consider to quit trading.
There will be some people who will reject your assumption even though it is basically true, for people who are scientifically illiterate but very open to the name of profit they will not care about ideas that will hinder them. Many come because they are motivated by others who are successful and make huge profits from trading, they want to have the same fate but the problem is that they do not bring any preparation and fishing tools to get, isn't it nothing more than gambling? yes I would say that if anyone gets involved and enters the world of trading without having any understanding and knowledge, because they will only depend on luck.
With that said, I would agree with your statement that "trading is not for everyone", and I would add one thing "there is no instant wealth in trading". Before you jump in and get involved because you are motivated by the success of others then I hope you should first see what difficulties they faced in the process of achieving it, if you already know and have the answer then I'm not sure you will still be convinced to get involved. Basically, there are so many things you have to prepare, good planning, money management, emotional and psychological, patience, consistency and willingness to continue learning to improve. So think and consider again if you want to get involved.