Investing is a contrarian game. The only way to win in the long run is to see things that others have missed, finding the value in places where it has been ignored. It is certainly based on sets of objective criteria, but also comes down to the human judgment of how to weigh multiple and complicated factors and is, therefore, an ultimately subjective endeavor.

New investors are taught to “buy what you know.” This was especially en vogue during Peter Lynch’s heyday in the 1990s. The advice is not strictly false but can be wildly misleading. A 1999 feature in Fortune about Barbara Streisand illustrates this.

“Where does the singer-actress-director get her financial ideas? The same places as any investor–from friends, relatives, and daily life. “We go to Starbucks every day, so I buy Starbucks stock,” she explains. (Streisand also gave some Starbucks shares to her longtime housekeeper recently as a birthday gift.) Another pick is Time Warner (the parent company of this magazine), which Streisand has held since 1992.”

“Buying what you know” is not the same thing as simply purchasing the stocks that are most relevant to your own life, as Streisand did by buying Starbucks stock simply because she went there every day. It involves dispassionately understanding what gives a particular business a competitive advantage and using your familiarity to get an edge on others in appropriately valuing the company.

Since so much of our investing decisions are subjective, one of the primary keys to success lay in understanding yourself. Which biases are you most prone to fall victim to? Where do your blind spots lie? As politics become increasingly polarized, more and more investors are finding that their blind spots lay in how they translate political beliefs into investment decisions. I became entangled in a case study of this phenomenon.

A little more than a year ago, I took a look at the firearms industry. The growth had been monumentally explosive for years. Between 2002 and 2016, the number of background checks performed by the FBI more than tripled. I wanted to know if this growth was sustainable and if not what that would mean for stocks in the sector.