It's great to get advise from financial planners, advisors etc. who tell you to diversify your portfolio so you don't get hit hard if/when a particular sector goes out of flavor, but really, how practical is that, esp. if you are managing your own money? There's so much news and research to do to keep abreast on specific industries (let's say technology, media/entertainment, advertising etc.) that if you started diversifying beyond more than 3 or so industries, you'd spend all your time doing research instead of managing your portfolio. And even then you won't be able to keep up with your news and latest happenings. All the success stories that you heard about (traders, investors, entrepreneurs, businesspeople etc.), they are successful because they are amazing at what they do. A media executive/investor isn't going to start focusing on energy all of a sudden and become a top executive in that industry. Could it happen? Yep, but why bother? Why not just continue to focus on those industries and be an expert? What do you all think?