Children are most susceptible to emotional responses because they do not know better. Reason requires the ability to predict the outcomes of your actions, which in turn, requires experience. This is why we do not allow persons below the age of majority to partake in certain activities that require better decision making, such as driving or voting.
Most adults, however, are expected to have the ability to use reason (a magical ability that shows up the day you turn 18). But logic, you see, is hard work. Use of reason in decision making requires you to weigh the pros and cons of each possibility. You must think through the outcome of every decision and how you plan on dealing with the worst case scenario.
And all that sounds so boring and tedious. It is just so much easier to give in to the lazier, emotional response, which doesn't hurt your brain as much. Which is why we have people shooting random strangers when they feel like their life is unfair, and families killing children who dare "dishonor" them, and teenagers killing themselves over a failed grade, and rejected men thinking that burning the face of a woman who dared reject them would somehow make them feel better about it.
On the other hand, we have people who use logic in every aspect of their lives, who may be making poor decisions themselves, because there are situations where emotions are more important. For instance, in selecting a mate, the rational way to choose would be to consider genetic compatibility, fertility and financial means. None of these however guarantee marital happiness, because that is inherently an emotional decision. As is the decision of dropping everything to drive a hundred miles when your best friend or a family member needs you to be there for them.
So maybe to be truly rational, one must know when to use reason and when to be guided by emotion.