A wealth of utterly timeless wisdom is found in Edwin Lefevre's 1923 classic Reminiscences of a Stock Operator. Here's a sample: (emphasis mine)
It is the way a man looks at things that makes or loses money for him in the speculative markets. The public has the dilettante's point of view toward his own effort, the ego obtrudes itself unduly and the thinking therefore is not deep or exhaustive. The professional concerns himself with doing the right thing, rather than with making money, knowing that the profit takes care of itself if the other things are attended to.That said, contrary to Lefevre's protagonist's suggestion, I don't know that it's lack of deep or exhaustive thinking on markets that (save perhaps for the housebound day trader) necessarily explains the (as popular opinion has it) lack of success of the 21st Century average do-it-yourself investor. I do, however, agree that it's how one "looks at things" that makes or loses one money. My observation is that when markets get squirrely, the individual investor tends to look at things through the eye of emotion and, thus, abandons the consistent long-term balanced approach that would otherwise, and successfully, be attended to.