Leave the serious thinking about strategy adjustment, observations, etc. for in between points, when you are catching your breath or preparing for the next point. That's where the bigger decisions should be made and where you decide if you are going to try and set anything up.
During the point, I think you should rely mostly on instinct but also try to execute your gameplan when the spots are available.
Lastly, I think "instinct" can be built up by practicing. For example, you can train yourself to recognize balls that you should and should not be taking risks with and attacking during practice so that when these situations come up during the match, your "instinct" is there.