NEW YORK ( TheStreet) -- One of the things that I enjoy the most about the financial markets is that there are few "gray" areas. More than any other business, what you see is usually what you get.You can look at debt on one side and equity (if you're lucky) on the other. On one page there is either a profit or a loss. The financial scale will always favor one side over the other -- that's why it's called a balance sheet. Hip-hop king, Jay-Z once said, "Women lie, men lie, but numbers don't" -- it can't get any more fundamental than that. So why is it that those whom we trust to manage our money are always looking for justifications for their losses? I will argue that you should fire any financial expert who finds a way to justify a poor portfolio performance. Don't give it a second thought. Today it is popular to blame the IPO underwriters or Facebook's ( FB) management for losses incurred in that stock. I guarantee you plenty of managers will blame both at the end of the year. Before the recent improvement in Sirius XM's ( SIRI) stock price, managers were quick to blame the stock's poor performance on writers like me, short-sellers, daytraders, hedge funds and anyone else that had anything negative to say. It's always been easier to pass the buck during the bad times, but managers want to be considered celebrities when the good times roll. Not so fast. In the first part of this series, I talked about the importance of making investment decisions more about the bottom line and less about the sometimes unspoken myths that yield little in the way of results. In the second part, we looked at the myths surrounding portfolio diversification. Part 3 reminded us that there's a sucker born every minute, while part 4 noted that valuation often means nothing when assessing a potential investment. Because part 5 discussed the myths associated with the so-called "smart money,", I have decided to now look at those whom we have entrusted to manage our finances: those whom we think are smarter than us but are often quick to justify why they performed so poorly.