One of the most common shortcomings I see among investors is the inability to (a) pick a system that fits their investing personality, and (b) to stick to that system, even after a few less-than-stellar months. Both are actually closely related. The first of those is pretty easy to understand—if the system an investor chooses to implement regularly results in, say, huge drawdowns from time to time, yet that investor has trouble keeping his wits about him after a bad day or two, he simply won’t be able to stick to that system over time. The same goes for...