Really all these books, quotes and studies are a waste of time regarding trading particularly, maybe apply better to other areas of life. Trading is highly individual and there's so many factors that go into someone making it into trading. Skill, intelligence, personality, when they started in life, capital, do they have another income stream coming in while they are learning trading, luck, what was market like when they started, what strategy or learning path they went down, are they naturally bullish or bearish bias. Maybe being too pessimistic actually hurt someone, while being too optimistic hurt someone else.
Seems a lot of people look to correct emotions from a mental side, or read some book or something all I can say is that doesn't work for me. The only thing that improves my mental is making physical and tangible changes. Like making sure I actually have an edge. Setting up my screens better or coding so that information is more readily available. Making sure I am not overly concerned about money while trading (by having money in reserve). But hey if reading a book or looking into studies actually provides value to others, fair enough. Just don't do jack for me.