If I learned anything during the time that I ran my Real Money Portfolio, it's that diversification really does matter.

This is a lesson that you are always told when starting out as an investor – to spread your investments out across multiple asset classes, companies, geographies and sectors. Overall, I think the Real Money Portfolios achieved proper diversification, however my particular portfolio was specifically focused on the energy and materials sectors by design.

At first, things were humming along swimmingly. I plugged in my first investment in May 2013 at a time when oil prices were riding above $90 per barrel (and quite often $100), China's growth story was still very much intact and OPEC hadn't yet stirred the pot.

As things progressed, I diversified into several sub-industries of these two cyclical sectors.

I dabbled in the iron ore industry with Vale SA (NYSE:VALE) and Cliffs Natural Resources (NYSE:CLF). Geothermal energy entered the fold with Ormat Technologies (NYSE:ORA) – my portfolio's highest performing stock. I gathered up my first oil-related shares with EOG Resources (NYSE:EOG). And chugged along with a few other recommendations, ending with a double-down on residential solar by way of SolarCity (NASDAQ:SCTY).

Overall, I was quite proud of the selection I had put together. Dividend-paying heavyweights like Freeport-McMoRan (NYSE:FCX) and Canadian National Railway (NYSE:CNI) gave me exposure to the mining industry. Complementing them, I purchased intriguing mid-caps like Albemarle Corp (NYSE:ALB) and growth options like SolarCity, and suddenly I had a diversified energy and materials portfolio.

Unfortunately, all of that diversification went up in smoke last November when OPEC decided it wanted to start a price war in the oil field. Needless to say, when the price of oil gets cut in half, so do the market values of the majority of those exposed.

As a result, my portfolio ended up vastly underperforming the S&P 500 benchmark. I just didn't have the benefit of owning exposure to the healthcare sector that is up over 24% in the past year. Or, heck, I'd have even settled for the performance of the industrial sector, which is up 4% since August of last year.

Instead, I was saddled with the energy and materials sector sell-offs to the tune of -28% and -6% over that same time frame.

Looking forward
Now, please don't take this downtrodden performance as any indication that I would immediately sell all of the positions in my portfolio. No, I do believe that the oil markets will rebound. I also believe that it might just take a year or more to do so.

Thankfully, if all goes according to plan, I have more than a year's worth of investing ahead of me. That's why I have listed the top five stocks from my portfolio that I'd be more than happy to continue holding or even add to as things turn around.

(In alphabetical order)

- CN Rail

- Core Laboratories (NYSE:CLB)

- EOG Resources

- SilverWheaton (NYSE:SLW)

- SolarCity

Not only do I have faith in the management teams behind these companies, but I believe they are, or are quite near, the very best in their respective industries. (I have personally interviewed the CEOs of CLB and SLW, along with the VP of Investor Relations at CN Rail.) I haven't lost faith in them, and if you're a shareholder, I'd recommend you consider staying the course as well. Of course, everyone's situation is different, but the long-term shareholder in me will be giving all five another thumbs-up in Motley Fool CAPS.

Foolish bottom line
It's nearly impossible to predict when disaster will strike like it has in the oil patch. These things are capable of happening in any specific sector or region of the world, hence the droves of investing professionals and academics stumping for broad diversification. This lesson has certainly been branded in me for the rest of my life.

I hope this lesson comes a bit more cheaply for you than it did for me, but I appreciate The Motley Fool for encouraging me to learn it. In the meantime, I'll be tracking this selection off the record to see how it performs once things do begin to turnaround along with counting my blessings that I'm able to work where I do.

Onward!

Editor's note: The Motley Fool launched its Rising Stars Portfolios program in late 2010.Twenty-five analysts took part in this endeavor,  investing hundreds of thousands of dollars of The Motley Fool's money in hundreds of stock ideas. With the analyst tally in the program now called Real-Money Stock Picks down to four, the Fool has decided to close the remaining portfolios. It's a logistical decision and no reflection on the analysts or their stock ideas.

The Fool will keep some stocks chosen by the analysts in a Robert Kirby-like Coffee Can Portfolio. We're going to hold them, for a long time, without checking in, without trading. We count the Real-Money Stock Picks program a success in our mission to help the world invest better. 

Sept. 18, 2017: The Motley Fool intended to hold some Real-Money Stock Picks stocks, but this turned out to be a logistical burden, so the stocks were sold. 

Taylor Muckerman owns shares of Core Laboratories and SolarCity. The Motley Fool recommends Canadian National Railway, Core Laboratories, and SolarCity. The Motley Fool owns shares of Canadian National Railway and SolarCity. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.