It's a common misconception that acting rationally means eradicating emotion from our thought processes.  Indeed, the opposite is the case, as psychologist Nathaniel Branden observes.  Our greatest ideas are ones that we feel deeply, that resonate with us.  That is what traders mean when they refer to having "conviction" in a trade.  Our worst trading occurs when we feel things and react to those impulsively.  In those cases, our reacting prevents us from reflecting and thinking clearly.  Everyone feels uncomfortable when markets move against us.  The question is whether you use those emotions as information or allow them to control your next actions.

Most traders have had the experience of looking at market information, discussing ideas with others, and scouring research and suddenly see where things are lining up and making sense.  That aha! moment is a great example of feeling deeply.  Our greatest ideas are ones that come to us with that deep sense of recognition.  Those are the ideas we're meant to act upon.  Acting means directing ourselves toward a chosen end based on all the information available to us:  factual information and also information from our deepest feelings.

When we react, we are not directing ourselves toward a chosen end.  Rather, we are allowing events to control us and dictate our actions without planning and without conviction.  Little wonder that some of our worst trades come from decisions made out of fear, greed, FOMO, etc.

We think most deeply when we quiet our minds and shut off our internal chatter.  It's when our minds are still that patterns in the world can come to us and give us that sense of aha!  A quiet mind is an open mind and an open mind is ready to feel deeply.  One of the greatest edges in trading is the ability to approach markets with a still, quiet mind.