That is, if you are holding 400 shares of a stock, at the next point at which to add, add no more than 100 or 200 shares. Think like a guerrilla warrior. We wish to fight on the side of the market that is winning, not wasting our time and capital on futile efforts to gain fame by buying the lows or selling the highs of some market movement. Our duty is to earn profits by fighting alongside the winning forces. If neither side is winning, then we don't need to fight at all.
Trading is a common-sense business.
When we trade contrary to common sense, we will lose. Perhaps not always, but enormously and eventually. Avoid complex methodologies concerning obscure technical systems and trade according to the major trends only.