Nice article that explores the mental bias that effect trading

http://theweek.com/articles/442856/7-mental-biases-that-could-impact-how-invest


Even pundits have a hard time pinpointing the market forces that can possibly explain why 'tis the season for skittish investors.
But there is one thing that seems indisputable: There's no shortage of brain forces at work.
Maybe the end of summer makes you feel less relaxed, or perhaps the anticipation of Halloween is unearthing hidden fears about your investing strategy. Whatever the case, the psychology of investing says you have naturally held cognitive biases that could affect the way you make decisions about your portfolio … whether you realize it or not.