Tom Gardner, co-founder and CEO of The Motley Fool, says in an interview with Forbes that two of the most important things an investor can do are being open to learning from other successful investors, and taking a long-term view of the stock market.

Gardner, who founded The Motley Fool online community with his brother David, was bullish earlier this year when many were pushing apocalyptic viewpoints; since then, the market has surged. “It’s tough to do, and it was,” he said of staying disciplined. “It’s sad to see your portfolio go down, but you really have to train yourself to look at it in 10-year cycles. And I think, obviously, this has not been a great last 10 years. But, all in all, when the market is down, that’s the time to get excited. And when the P/E and all the multiples on earnings across the market are north of 20, that’s a time to get concerned.”

Gardner also discusses why he’s a big believer in fundamental analysis, why he thinks it’s critical to invest in companies with good management (and how he assesses that), and what he might do to change Wall Street — an entity of which he’s been very critical over the years.