My and Jim Cramer's emotion. Because, even if we say we're not emotional, at some level, we all are. Even if you take profits or you buy the dip or you act all aloof and indifferent, emotion drives who you are. Don't fool yourself. You can't escape emotion. The most straight-faced, hardcore, disciplined day traders -- emotional beings. It's not about whether or not you're emotional; it's about how you control that emotion. In investing, this process of control must be constant. It's focus No. 1 from position entry to position maintenance to exit. You bought AAPL at $XXX and you will sell this much at $XXX (on the up or downside). You're scaling into your position at X levels Y times a month, quarter, year and you will scale out when this or that happens. Whatever. Have a plan. Write it down. And hold yourself to it when the time comes to act. No regrets if you leave money on the table or the thing ends up running after you sell. Over the long run, this type of discipline protects traders and investors from catastrophic losses.