When we react to something, it's knee jerk. It's off the cuff. Spur of the moment.
There was a woman who had gossiped and spread rumors about another woman in the Church and it hurt the other woman terribly. Upon finding that what she had spread was untrue she went to the preacher and asked what she could do to make things right. The preacher told her to get a feather pillow and take the feathers and spread them about as she walked around town. She did so and went back to the preacher to tell him that she had done what she was told. She asked what she was to do now. The preacher told her to gather the feathers up again. She said "Why, that's impossible!" The preacher said, "So it is with the spoken word. Once spoken they can never be gathered back."
When we respond to something, the response is considered first in light of what would be best. It's the old "count to 10" method of diffusing emotion before something thoughtless is done or said. Once we learn to stay in the moment and consider situations that present a challenge, we will do so much better and respond rather than react.
Have you ever been caught off guard when arriving home and the package of cookies is right there on the bar and you are so hungry? You go to a meeting and the refreshments are right there and everyone is lining up to partake. A friend calls up and wants to go out to eat somewhere and catch up. We often go along to get along thinking we might hurt someone's feelings or be in an awkward situation if we don't follow our old habits and reactions. How can we be proactive? What do you do to stay with your plan?