In this choppiest of stock markets, it's very easy to get discouraged. The S&P 500 just had its worst month of the year, the Facebook initial public offering was a wreck, and all those rumors out of Europe aren't helping anything.
Okay, so maybe we can't all be John Paulson. The hedge-fund kingpin famously made $15 billion in a single year by betting against the housing market, inspiring the book "The Greatest Trade Ever".
RELATED: 9 Common Mistakes Investors Make
But let's take a page from another book and draw on Norman Vincent Peale's "The Power of Positive Thinking".
We talked to a few prominent market watchers about the best investments they ever made. What they picked, how they picked it, and what they ultimately learned from it.
We all have our investing successes, even if they're relatively modest. By learning from other people's home runs, here's hoping we can hit a few ourselves.
Name: David Rosenberg, Chief Economist and Strategist, Gluskin Sheff
Investment: Bonds and gold
The story: "The best strategy call I ever made in my career was what I refer to as the 'bond-bullion barbell'. It basically means having exposure to two types of assets -- bonds and gold -- that serve as refuge in this tumultuous post-bubble deleveraging cycle. I've been on that for a decade now, and they've been wonderful safe havens. They're natural hedges; gold hedges against inflation, bonds hedge against deflation. Nothing moves in a straight line, of course, and there have been corrections along the way. But bonds and gold are in secular bull markets, and when you can identify big long-term trends like that, the clouds part and help you make great decisions. Some people think you can only make money in equity bull markets, but that's just not true."
What he likes now: Corporate bonds -- Thanks to strong balance sheets and minimal default prospects. "The high-yield market now offers an 8 percent coupon on average, which in my view adequately compensates you for any recession-induced delinquency risks."
Name: Robert Shiller, Yale University economics professor and author of "Irrational Exuberance"
The story: "I made the decision in the early '80s to invest 100 percent in the stock market. At that time the market was priced very low, because people were overreacting to high inflation and interest rates. In times like those people don't tend to want stocks, because they can get high returns on bonds or even savings accounts.
So the average price/earnings ratio for stocks was around six, which I thought was grossly underpriced. Eventually I pulled most of it out in the late '90s, when the stock market experienced a bubble and became totally overpriced. In the meantime, I made something like 10 times my money. When big events like that happen, you can time the market."
What he likes now: A very conservatively positioned portfolio. "Stocks are still my biggest single holding, but I'm worried because they seem highly priced. My inclination is to stay in the market, but to not be aggressive about it."
Name: Conrad Herrmann, senior vice president, Franklin Equity Group
The story: "We originally bought Apple in 2003, when it was priced in the teens. Now it's one of the biggest companies in the world, and priced at almost $600, but it actually had a relatively tiny market cap at the time. It only had three percent of the computing market, but we liked its fundamental characteristics, and thought it could gain some market share. They had just launched the iPod, but this was long before revolutionary products like the iPhone or the iPad.
Most importantly, Steve Jobs had come back to the company. Jobs was a real visionary, and an agent of transformational change, who some people compare toThomas Edison. Back in 2003 the company's future wasn't clear, and you never really knew what was going to happen. But it turned into a once-in-a-lifetime investment opportunity."
What he likes now: U.S. equities. In particular "the technology sector, where companies can focus on doing more with less. Also companies that can either maintain margins, or continue to increase margins through pricing power."
Name: Barbara Corcoran, founder, The Corcoran Group
Investment: Manhattan townhouse
The story: "It was 1981, it was a townhouse at 49 E. 10th St. in Greenwich Village, and I tried absolutely everything not to buy it. I was desperate to open a small brokerage office in the Village, because I felt the neighborhood was turning around and was going to explode.
I hunted everywhere, couldn't find anything, and finally saw a 'For Sale' sign on this six-story building with 10 apartments. The broker refused to rent the ground floor to me, but said he would sell it to me for a little under a million bucks. I had never signed a mortgage in my life, but for some reason a bank loaned me 95 percent of the money.
The other day I had it appraised at $7.7 million, and it still makes me a 20 percent profit, year after year. It's the little building from heaven. I've bought many buildings in Manhattan over the years, but no investment has done nearly as well as that first one."
What she likes now: Investing in small businesses, everything from cake companies to medical-device manufacturers, stemming from her role in the ABC series Shark Tank. "I'm finding it far more exciting to roll up my sleeves and help young entrepreneurs build their fortunes, instead of checking out boiler rooms."
(The writer is a Reuters contributor. The opinions expressed are his own.)