This is my 3,000th column. I've learned a tremendous amount in writing about investing and the economy. Here are a few of the big lessons.

I've learned that changing your mind is one of the most difficult things we do. It is far easier to fool yourself into believing a falsehood than admit a mistake.

I've learned that people are terrible at predicting their own emotions. You will be more fearful when the market is crashing and more greedy when it is surging than you think.

I've learned that strong political beliefs in either direction limit your ability to make rational decisions more than almost anything else.

I've learned that short-term thinking is at the root of most of our problems, whether it's in business, politics, investing, or work.

I've learned that debt can cause more social problems than some drugs, yet drugs are illegal and debt is tax deductible.

I've learned that finance is actually very simple, but it's made to look complicated to justify fees.

I've learned that self-interest is the most powerful force in the world. People in unethical, predatory, and nonsense jobs will do mental gymnastics to convince themselves they're doing the right thing. Those who criticize the behavior of "greedy Wall Street bankers" underestimate their tendency to do the same thing if offered an eight-figure salary.

I've learned that people are twice as biased as they think they are, which is precisely why biases are dangerous.

I've learned that unsustainable things can last years, even decades, longer than people think.

I've learned that those who think "it's different this time" are the four most dangerous words are wrong. It is always different this time, as no two recessions, recoveries, or market cycles are alike. What's dangerous is assuming the future will perfectly resemble the past.

I've learned that journalists' need to write far exceeds the number of things that need to be written. No writer can say to their boss, "There's nothing important to write about today," although it is the truth most days.

I've learned that no one cares how accurate pundits' forecasts are. Those who listen to pundits are most interested in having their own views confirmed. Accuracy is an afterthought.

I've learned that there's a strong correlation between knowledge and humility. People who spend 10 minutes on Google studying monetary policy think they have it all figured out, while people with Ph.D.s and decades of experience throw up their hands in frustration. The more you study economics, the more you realize how little we know about it.

I've learned that what looks like tomorrow's biggest threat almost never is. Most of what people worried about over the last five years -- inflation, rising interest rates, a double-dip recession, stagnant markets, Greece leaving the euro, a government default -- never occurred. The biggest actual risk for most of us was something few talked about: excessive pessimism.

I've learned that data can do more harm than good. There is so much data available today that you can convincingly prove almost anything by cherry-picking with industrial strength. This breeds confirmation bias, as people start with an answer then find data to back it up.

I've learned that a willingness to wait longer than other people is your biggest natural edge. If you can think about the next five years while everyone else is fixated on the next five months, you have an advantage that makes high-frequency trading, insider tips, and corporate loopholes look like a joke.

I've learned that we can't tell the difference between luck and skill. Out of millions of investors, a few will be phenomenally successful due to luck alone, yet no one is willing to admit they are one of the lucky ones.

I've learned that there's no such thing as a normal market or a normal economy. Some people spend their lives "waiting for things to get back to normal" without realizing that stocks and the economy are always in some state of craziness.

I've learned that when it comes to earning high investment returns, market volatility is like an entrance fee at an amusement park. But few investors want to pay the market's entrance fee. They'd rather sneak in the back door, hop the fence, and outsmart security -- all of which is stressful and likely to fail. At both the amusement park and in investing, they'd have a better experience if they just paid the damn entrance fee.

I've learned that Winston Churchill was right when he said, "You can always count on Americans to do the right thing -- after they've tried everything else." Congress is a basket case 99% of the time, but when things are truly at the precipice it gets things done.

I've learned that people's expectations grow faster than their wealth. The country is richer than it's ever been. I don't think it's as happy as it's ever been.

I've learned that how you reacted to past bubbles is a good indication of how you'll act to future ones. The same people buying dot-com stocks in 1999 were buying Miami condos in 2006 and gold in 2011.

I've learned that "do nothing" is the best advice for almost everyone almost all the time.

I learned that Godwin's Law is totally accurate.

What about you?

For more: