Thinking errors, are systematic deviations from rationality, from optimal, logical, reasonable thinking and behavior. The word "systematic" is important because we are often wrong in the same direction. For example, it is much more common for us to overestimate our knowledge than to underestimate it.
Or the risk of losing something: it gets us going much faster than the prospect of gaining something. A mathematician would speak of a "skewed" (asymmetrical) distribution of our reasoning errors. Fortunately, the asymmetry sometimes makes mistakes predictable.
In order not to frivolously gamble away the fortune that I had amassed in the course of my writing and business activities, I began to make a list of systematic errors of thought, including notes and personal anecdotes.
With no intention of ever publishing it. I did this all to myself. I soon found that this list was useful to me not only in investing, but in business and personal life as well. Knowing about the wrong thinking made me calmer and more prudent: I recognized my own thinking traps early on and was able to avert them before they had caused great damage.
And for the first time I understood when others were acting unreasonably, and was able to face them well - perhaps even with an advantage. But above all, the specter of irrationality was banished - I had categories, terms and explanations to hand to scare it away. Thunder and lightning have not become rarer, weaker or quieter - and so have been with my own irrationality ever since.