If not handled in a healthy way, you could hurt someone you care about.
As human beings, we will always have reactionary responses when faced with conflict, action, or certain circumstances. It is up to us to make the choice of how we react, but based on who you are, you are either more emotional or logical.
As a person who acts off emotion in the moment, it can do more harm than good if you don't know how to control it. It can cause you to lash out at someone you care about, say things you may regret later, or only look at the present moment instead of seeing how this could affect the future.
All of this being said, acting off emotion can be good too. It means that you are more empathetic than the average person. Having empathy means that you have the capability to understand the emotions and feelings of other people. When an emotional person is in a healthy and good state of mind, they can handle conflict very well, and be there for other people.
For someone who tends to act off logic, this can look much different for you. Using logic to deal with life can make you come off as more stable, however, it can cause the following you to not be able to emotionally understand someone else, be defensive, and be unable to express how you are really feeling through words or actions.
I have had many interactions with people who are more logical rather than emotional. They handle stress very well, however, they can come off as rude or as if they don't care about you when in reality they just are unable to express how they feel. If not handled well, this kind of interaction can end friendships, partnerships, and relationships.
Every personality is different, but anyone can fall into one of these two categories. People who are more on the emotional side need to take reign of their emotions and use this gift of empathy that they possess to help impact those around them and help other people feel heard and understood. On the other hand, people who fall into the logical side need to be able to healthily express how they feel so they can get their point across in the kindest way and help others to see their side of things in a way that makes sense.