I thought this was interesting. It is fairly common online, for people to claim they are being rational and make their decisions accordingly, when they aren't making any sense at all. People go with their emotions, then make up rational explanations later. In fact, I generally suspect interlocutors that pridefully assert how rational they are of being afraid of their own emotions, and I tend not to believe them anyway, when they say they are only being "logical".
Where rationality comes in handy, in decision-making, is to prevent one's emotions from leading into something really foolish. There are times when I know I have to keep my head in charge, because if I "listened to my heart", I'd end up in a world of hurt. However, if I am dealing with something *wholly* on a rational level, I often end up arguing myself into indecision-- and a lot of the time dealing with something purely on a mental level means mostly that it isn't all that important to me in the first place. There are always two sides to every argument, as the saying goes, and probably more. You risk doing something stupid when you're led by your emotions, but at least you'll do *something*.
Actually, I was just thinking tonight that if one has two choices, one can never go wrong by choosing the most compassionate way -- and that's not necessarily the direction one's emotions will lead. Compassion has nothing to do with sloppy emotion; it means you do the best you can for the other person, given the set of circumstances you are in. Justice and mercy are good guideposts in decision-making, too. Mostly folks do what they want to do, then convince themselves that it's right, or even that God wanted them to do it. Principle is a middle way between cold rationality and hot emotion; it partakes of both.