Aloha,
A reaction is instant.
It’s driven by the beliefs, biases, and prejudices of the unconscious mind.
When you say or do something “without thinking,” that’s the unconscious mind running the show.
A reaction is based in the moment and doesn’t take into consideration long term effects of what you do or say.
A reaction is survival-oriented and on some level a defense mechanism. It might turn out okay but often a reaction is something you regret later.
What is a response then?
Read more of my post on Psychology Today
https://www.psychologytoday.com/blog/focus-forgiveness/201609/react-vs-respond