most mistakes of traders are;
* Having no proper training in the craft to attain knowledge about it.
* Having no experience traders that is good in the craft to guide them.
Not everyone has an access to this so in a way it's not really a mistake on the newbie trader side, some people just started trading and they just gained their own experience through continuous losses and gains
This is the major reason most traders fail in
the trading, because no proper knowledge on the craft, or no knowledge to ascertain the sentiment of a candle sticks, they just dive unto the market blindly and start acting up when the market has taken them out.
if they try and find a school that does this exact thing, they're going to get nothing out of that because the market is volatile and they might not even use a lot of the stuff that they've learned in that school when the actual trading happens, mentors are expensive especially if you don't have a connection.
This is what i totally disagree on, the only way you are going to get nothing from a trading school is if they the teachers doesn't knows the craft or you as a person can't comprehend what you are being thought, because the candle sticks is just like a language telling you something about what the market is about doing next, so if you can't read the candle sticks or do technical analysis as we usually call it, you are bound to lose money in the market because at that state, you are diving into the market blindly.
Then as for mentorship, you are actually right on that aspect, it's quite costly, but if you have the financial leverage to afford it, invest that money on yourself because it's going to worth it in the very end.