In this video as part of our Ask a Fool series, Motley Fool One advisor Jason Moser takes a question from a Fool reader, who asks, "Why would a winning stock that has had a good run and now makes up a bigger portion of your portfolio, mean that there is a greater risk? Heard this argument on Market Foolery the other day. Doesn't make sense to me."

Jason Moser has no position in any stocks mentioned. The Motley Fool recommends and owns shares of Apple. 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.