Thinking and responding on the fly

As a therapist, it is an ongoing effort to be completely present and mindful in sessions.  We must tap into all of the cues our clients give us in any given moment.  While working my internship I realized that my style of processing thought was often to go away and think about things and bring them up the following session. I found this was less effective than if I was able to make these observations in the moment and so I consulted with my supervisor about it.  Over time I have been able to improve the ability to "think on and respond on the fly".  A quick whitted comeback can have quite an impact in everyday conversation or debate too.  I am interested to see what you all think of this ability and what it is that helps us to improve it.  Where else and how else can it be useful?  I would like this to be a discussion so please don't hold back :)