Rational behavior requires theory. Reactive behavior requires only reflex action.
To be reactive is very simple. Something happens, and you immediately do something to plug the gap. However to be rational, you must first assess if the plugging the gap immediately causes any downstream effects to whatever processes you have for your organisation, be it private or public.
In the world that we're living in today, we must try to resolve any issues as fast as possible but sometimes, we need to sit down and think clearly if the issue is a process issue, or a human issue. Are you making things worse by being reactive? Most of the time we are.