What is the Single Biggest Mistake That Keeps Investors from Reaching Their Goals?

Less than a month before he died in January 2012, founder & Managing Partner of Praetorian Value Fund Victor Fasciani was asked in an interview 'What is the single biggest mistake that keeps investors from reaching their goals?'  His answer:

"In my view, the biggest mistake investors make is to deviate from their original plan. This is not to say that one mustn’t diligently monitor their investments to determine if anything significant has changed within their holdings, or re-examine their thesis if they have made a mistake. However, in a world with a 24-hour news cycle, multiple outlets for “news” and information, including the Internet (websites, blogs, videos), it has become more important than ever to discipline oneself to tune out the noise."

While he was an active investor who tried to beat the market by picking underpriced stocks and was likely referring to money managers when talking about 'investors,' his answer applies to any method of investing both as a professional and as an individual.  It especially applies to the evidence-based model of asset class investing that we follow.

Let me repeat:  "However, in a world with a 24-hour news cycle...it has become more important than ever to discipline oneself to tune out the noise."

It's hard to put enough emphasis on how important this concept is to a successful investing experience.  Words of great wisdom that would all be wise to remember. 

Especially these days with the situation with the Greek economy coming to a head and a computer glitch stopping trading on the NYSE - as important as those things seem right now, they're all just noise for a long-term investor.