Mark Douglas is good. As is Ruth Barrons Roosevelt. Psychology books are a steal compared to other costs.
I would spare no expense in these books and courses.
People tend to overlook the psychological preparation to be a trader, the truth is without the right mentality you are doomed to failure.
Mechanical systematic auto-traders are also subject to psychological traps, like overfitting, turning systems on an off arbitrarily, but I haven't seen any psychology book for this kind of trader.
I have met systematic fund managers who think they are unbiased, mathematical, fully computerized, objective, but are as emotional and psychologically flawed as any newbie trading from the gut.
It's because they don't pay attention to this stuff, they think it's all worthless, but you are on the right path getting interested in Mr. Douglas' books.