I'm always interested in understanding the math of things and understanding as much as I can about all aspects of business. And what I learn today may be useful to me two years from now. That's really the wonderful thing about investments is your knowledge is cumulative.
You will be right, over the course of many transactions, if your hypotheses are correct, your facts are correct, and your reasoning is correct. True conservatism is only possible through knowledge and reason.
There are a few investment managers, of course, who are very good - though in the short run, it's difficult to determine whether a great record is due to luck or talent. Most advisors, however, are far better at generating high fees than they are at generating high returns. In truth, their core competence is salesmanship. Rather than listen to their siren songs, investors - large and small - should instead read Jack Bogle's The Little Book of Common Sense Investing.
Well, I think the biggest mistake is not learning the habits of saving properly early. Because saving is a habit. And then, trying to get rich quick. It's pretty easy to get well-to-do slowly. But it's not easy to get rich quick.
I would rather sustain the penalties resulting from over-conservatism than face the consequences of error, perhaps with permanent capital loss, resulting from the adoption of "New Era" philosophy where trees really do grow to the sky.
The commission of the investment sins listed above is not limited to 'the little guy.' Huge institutional investors, viewed as a group, have long underperformed the unsophisticated index-fund investor who simply sits tight for decades. A major reason has been fees: Many institutions pay substantial sums to consultants who, in turn, recommend high-fee managers. And that is a fool's game.
When you listen to tax-cut rhetoric, remember that giving one class of taxpayer a break requires - now or down the line - that an equivalent burden be imposed on other parties. In other words, if I get a break, someone else pays. Government can't deliver a free lunch to the country as a whole. It can however, determine who pays for lunch.
The big question about how people behave is whether they've got an Inner Scorecard or an Outer Scorecard. It helps if you can be satisfied with an Inner Scorecard.