One of the many great lessons that I have learned from the game of chess is when to think. Most people when they play chess, will think only after their opponent makes a move. The thought is, ok what do I do now? This is reactionary thinking.
The best time to really think is while it is the other players move, during their clock time. While they are pondering what to do after your move, you can now start to really formulate your plan. This is strategic thinking, something you do not get to do when you are just reacting.
Reactionary thinking is not strategic thinking. One of them you do under pressure, under constraint and with significant stress. The other you do when you do not have to. When you are not under pressure. Reactionary thinking is what you have to do, strategic is what you do voluntarily.
The interesting thing is that strategic thinking always produces better results, but requires you to dedicate time to do it. To use your spare time or to actually schedule time for this purpose. If you are just reacting you are going to lose to people that are strategic.
So you think when you do not have to. You think after you make a move and you are waiting for someone else to react. Instead of waiting for their response just so you can react again, do some strategic thinking and try to preempt their response. This puts you in a better position every time, you make your move quickly and put the burden of reacting back on the other person as fast as possible.