Year-end is rapidly approaching, which means it's time to review your investing or trading rules. Below, I have some time-honored advice that may help. Both Dennis Gartman and Bob Farrell are legendary traders, and they kindly shared the rules they’ve found most helpful. Both these guys are traders, rather than investors, but a lot of the advice is helpful regardless of the long-term strategy you use. NEVER, EVER, EVER ADD TO A LOSING POSITION: Adding to a losing position eventually leads to ruin, remembering Enron, Long Term Capital Management, Nick Leeson and myriad others. TRADE LIKE A MERCENARY SOLDIER: As traders/investors we are to fight on the winning side of the trade, not on the side of the trade we may believe to be economically correct. We are pragmatists first, foremost and always. MENTAL CAPITAL TRUMPS REAL CAPITAL: Capital comes in two forms... mental and real... and defending losing positions diminishes one’s finite and measurable real capital and one’s in...