On this episode of Motley Fool Answers, Alison Southwick and Robert Brokamp are joined for a very special podcast crossover event by Motley Fool co-founder (and host of Rule Breaker Investing) David Gardner. The hook? The Brothers Gardner will this week release the third edition of their now-classic tome, The Motley Fool Investment Guide, updated and revised for the world we're investing in today. And in that world, where change is rapid and tastes are fickle, David reminds us that the calm and measured temperament wins. In fact, he suggests, when you invest, treat your portfolio companies more like you would your favorite sports team.

A full transcript follows the video.

This video was recorded on Sept. 5, 2017.

David Gardner: So we just talked about buy, and hold, and hold, and hold, and ultimately that's a lot about how you think and then what you do or don't do based on what you're thinking.

So temperament is what you think, and I guess the much briefer story that I'll tell here is just the story of the word "invest," because the story of the word "invest" is that it comes from the Latin investire. I never did take Latin. By the way, I know, I have to believe, I'm going to guess, first of all, Robert, that you took Latin at some point.

Robert Brokamp: I didn't, actually.

Gardner: Alison, did you? OK, so none of us did, because ...

Alison Southwick: Rick says that he did.

Gardner: Rick did. OK, good. And I know some of our listeners took up to maybe Latin V, and others were glad that they never had to take Latin. I never did take Latin, but I do love language, so in some ways I regret that I didn't.

But the way that I make up for it is that I look at the etymologies of words. That would be, like, down on my tertiary list of it's definitely not a superhero power. It's more like a lame following. It's like I'm about as good at this as I am at fishing, which means I'm not good at either, but I care about it. Actually, I care about it more than fishing.

So the etymology of this word investire, the Latin, meant basically "to put on the clothes of." That's where our word "invest" today comes from. And so to me, that's my temperament. That's my mentality. When I buy shares in a company, when I invest, I think of myself as kind of, sports fans, putting on the home-team jersey. And I'm going to keep that jersey on. It's my team. I'm a part owner. It's actually even better than your sports team. Like you might be a Green Bay Packers fan. You might be a New York Yankees fan. When you buy shares of a company, you're actually a part owner of that thing. You're just kind of renting the awesomeness of being, let's say, a Packers or Yankees fan when you wear that shirt. But when we buy shares of public companies, we become part owners, and that's really important to me.

That's the way I think everybody should think about the markets, but it turns out we're in the minority, which is why we call ourselves capital-"F" Fools and why we write a book like The Motley Fool Investment Guide, because you're going against the conventional wisdom. You're being a Fool if you think that it's like putting on the home-team jersey and staying by your team.

But I think we just talked about the value in the previous point of staying by your team. And so I want people to have that mental image of putting on the clothes of Under Armour. Well, sometimes literally if you own Under Armour, which by the way has been a painfully bad stock for about 18 months now.

But whether it's an actual apparel maker like Under Armour or -- we just talked about it -- NVIDIA, which you can get a T-shirt probably somewhere on the internet for, think of yourself as "donning the clothes of" and stay by that team. Watch them each day if you're really a fan like I am, and I don't mean day trade. I mean I enjoy following the stock market. Or just check in once a year. But don't change your home team unless you have a real good reason to.

Alison Southwick has no position in any of the stocks mentioned. David Gardner owns shares of Under Armour (A Shares) and Under Armour (C Shares). Robert Brokamp, CFP has no position in any of the stocks mentioned. The Motley Fool owns shares of and recommends Nvidia, Under Armour (A Shares), and Under Armour (C Shares). The Motley Fool has a disclosure policy.