Proactive and reactive thinking are more than just two ways of thinking. Rather, they are a whole life philosophy. They are ways of looking introspectively and at the world outside of yourself. Most successful people think proactively first and reactively second.
Proactive thinking looks ahead to the future. It is the anticipation of an event that is known to happen. Reactive thinking is just that: an event occurs, and you react to it. Proactive thinking is preferred for many life situations, such as bill paying.
In proactive planning you must think about what to do before events happen, like planning your finances for a possible lay-off. You make choices and decisions based on your thinking.
Management consultant Edward de Bono stated that many intelligent people are not good thinkers. He states that many do not have "generative thinking." They are good at understanding and presenting facts, but not good in idea generation and development.
The significance is that proactive thinking leads to success, since you plan for the future. Reactive thinking is always one step behind, scrambling to fulfil a requirement. Proactive thinkers control the world around them. Reactive thinkers are controlled by the world.