This article is part of our Rising Star Portfolios series.

Math is a funny thing. If an investment loses 50% of its value, you need it to rise 100% just to break even. Unfortunately, we can't avoid this by choosing only investments that go up -- that's simply impossible to do. But we should endeavor to eliminate making dumb mistakes and stack the odds of success in our favor.

Early in my investing career my biggest mistakes came from investing in story stocks. You know the kind: hot product (think Crocs), quickly growing end markets (think FARO Technologies), and many more. In each case, the story behind the stock was so snazzy that I let slide that the numbers and the logic behind the business didn't add up. Painful lessons learned.

My now refined style of investing, having been tried and tested managing an investment fund, seeks to eliminate the likelihood of being blinded by a company's story. By focusing on companies that are unpopular, unattractive, or unknown, I can avoid making those costly mistakes. In cases where the "un" rules, it forces me to think independently, engage in dispassionate analysis, and ask the right (long-term, business-focused) questions. I call it un-vesting, so I've appropriately named my Rising Star Portfolio the Un Portfolio.

Sure, this means I end up looking at some pretty boring businesses. But good companies operate in unsexy industries. Good companies have mishaps and become unpopular. And good companies can be purchased on the cheap.

My first purchases have focused on out-of-favor sectors (health care and defense) where temporary factors are creating bargain opportunities. Shares of medical technology company Medtronic (NYSE: MDT) are priced as if the company's innovation engine is coming to a halt, which just won't happen considering that employee bonuses are tied to successful research and development activity. And defense contractors ManTech International (Nasdaq: MANT) and SAIC (NYSE: SAI) play key roles in cyber security and government IT -- growing markets that are well protected from budget cuts.

I urge you to hone your investment process, perhaps becoming an un-vestor yourself. If nothing else, following the Un Port will provide a variety of stock picks that will encourage you to focus on the investment's merits and not its story or the prevailing viewpoint.

This article is part of our Rising Star Portfolios series, where we give some of our most promising stock analysts cold, hard cash to manage on the Fool's behalf. We'd like you to track our performance and benefit from these real-money, real-time free stock picks. See all of our Rising Star analysts (and their portfolios).