The superfluous can be unnecessarily distracting from that which is both essential and adequate.
Warren Buffett on Focus
"One word that accounted for Bill Gates' and my success: Focus"
Definition of Focus
"When you think about focusing, you think focusing is about saying yes. No. Focusing is about saying No."
Jony Ive on Steve Jobs
Jonathan Paul "Jony" Ive — Chief Design Officer of Apple — explains how focus to Steve Jobs meant not just saying no to unimportant things, but sometimes even to a few important ones.
Focus vs Diversification
Warren Buffett has also spoken extensively in the past about how excessive diversification in one's investments can be counterproductive. Serenity too does a complete 17-rule Benjamin Graham analysis and nothing more.
This is based on the same kind of conviction in Graham's framework that Buffett, Seth Klarman and Irving Kahn have expressed.