Emily Flippen

I'm sure a lot of those sales probably felt rational at the time.

I always think to myself before I try to make these decisions, what key components am I missing?

What change or sentiment can drive that growth that I really didn't fully appreciate at the time?

It's important to reflect and recognize where I went wrong.

Jason, I'm hoping you can talk to me a little bit about the quantitative angle of selling.

In particular, why it can be so bad for a portfolio to sell a stock that ends up being 100 plus bagger rather than just holding on to a bunch of stocks that do ultimately go to zero.

How does the math work there?

I love the way you say that, Jason, and that's the way the market works, too.

It's easy for people to forget that when you buy an index fund, that the majority of companies underperform their own index.

It's those handful of companies that go on to produce massive returns that results in virtually all of the gains of the stock market.

I'm looking at my personal portfolio.

I pulled it up while you were talking, Jason, on Fidelity.

And I'm outperforming the market by about 1% this year.

But if you actually look at some of my individual companies, I see a lot of red, a lot of stocks that I have lost 96%, 95%, 73%, 78%.

I'm just reading off the numbers in front of my screen here.

But the ones that have done well have more than made up for it.

After the break, we're going to be flipping in the script and talking about when selling actually does make sense and how to build a framework that can help us stay invested as winners.

Stick with us.

Welcome back to Motley Fool Money.

To round up the show, I want to make sure that we don't leave people with the idea that the only Foolish move is to hold everything forever, no matter what.