You spend years trying to learn new stuff but then look back and realize just a few big ideas changed how you think and drive most of what you believe.

A few ideas that had a big impact on how I think about investing:

Markets have to be pushed to crazy extremes once in a while, but it’s never as crazy as it looks. It’s the result of five innocent things playing out:

Investors have different time horizons. Day traders, generational buy-and-holders, and everything in between.

Each group tries to exploit profit opportunities within their own timeframe.

Short-term investors are often after momentum. They can reasonably chase prices higher even when those prices are detached from a business’s intrinsic value.

Sometimes that momentum, and those profits, are strong enough to capture the attention of investors with longer time horizons whose strategy relies on businesses trading at or near their intrinsic value.

Things get crazy when the actions of long-term investors playing one game become influenced by the actions of short-term investors who are playing a different game and appear to know something the long-termers don’t. The long-termers usually don’t realize this, which is why the process is both innocent and bewildering, even in hindsight.

When viewed this way, bubbles stop looking like the actions of crazy people and more like people being unwittingly influenced by false signals. Which hopefully helps you avoid those signals yourself.

Keeping money is harder than making money, because you can get rich by luck, but staying rich is almost always due to a series of good, hard decisions. The skills needed for getting rich and staying rich are often opposites—be bold and brave, then diversify and remain paranoid. Then there’s the mental momentum that getting rich creates that staying rich has to step in and try to block. It goes like this: The more successful you are at something, the more convinced you become that you’re doing it right. The more convinced you are that you’re doing it right, the less open you are to change. The less open you are to change, the more likely you are to trip in a world that changes all the time. I’d be more impressed with a Forbes list of billionaires ranked by longevity vs. amount.

Investing brings out the gullible side of people because the stakes are high and it’s hard to measure the odds of specific outcomes. So otherwise-smart people hang on the words of wild forecasts … just in case. If something has a chance of either destroying you or making you very wealthy and you don’t know how to measure what that chance is, it’s understandable that people default to high levels of credulity.

You can’t believe in risk without also believing in luck, because they are fundamentally the same thing—an acknowledgment that you are one person in a 7 billion player game, and the accidental impact of other people’s actions can be more consequential than your own. But the path of least resistance is to be keenly aware of risk when it affects you, and oblivious to luck when it helps you. Investors adjust returns for risk; never for luck. Companies disclose known risks in their annual reports; lucky breaks are rarely mentioned. The danger is that experiencing risk reduces confidence when it should merely highlight reality, which can make future decisions more conservative than they ought to be. Luck increases confidence without increasing ability, which makes people double down with less room for error than before. Realizing that luck and risk are ever-present and normal makes you accept that not everything is in your control, which is the only way to identify whatever is in your control.

There’s an art and a science to investing. Part of good investing is just arbitraging other peoples’ future behaviors, and those people—all people—make decisions with some facts and some dopamine. Figuring out what’s likely to happen next, to the extent it can be done, is the intersection of, “X is factually true, but people pay more attention to Y and respond by doing Z.” It’s a mix of the science of finance (earnings, discount rates, credit spreads) and the art of how people behave with that science (FOMO, extrapolation, embarrassment, career risk). I think it’s fine to make decisions for yourself, and assume others will make decisions for themselves, based on things that can’t be rationalized by data and facts. That’s how the world often works whether you like it or not. If you think the world is all art, you’ll miss how much stuff is too complicated to think about intuitively. But if you think the world is all science, you’ll miss how much people like to take shortcuts, believe only what they want to believe, and have to deal with stuff that is too complicated for them to summarize in a statistic. Another way to think about this: Investing is not physics, which is guided by cold, immutable laws. It’s like biology, guided by the messy mutations and accidents of evolution, constantly adapting and sometimes defying logic.

There are two types of information in investing: stuff you’ll still care about in the future, and stuff that matters less and less over time. Long-term vs. expiring knowledge. There’s so much information these days that it’s vital to align what you read with how relevant that reading will remain over time. Quarterly earnings are important, but their relevance declines over time and expires with a long enough time horizon. Same with economic news, market news, and many company missteps—asking whether news is important misses the bigger question of, “How long will this remain important given my strategy and time horizon?” I have a rule of thumb: Read more books and fewer articles. It’s not that articles are bad. But books tend to be about timeless principles; articles tend to be more newsy. And the only way to know what kind of news is relevant to you is to have a deep understanding of the principles that will have the biggest impact on your strategy over the longest period of time.