Well, of course it depends on the individual. I relate to what you are talking about though. In some cases I really don't want to say too much at all because I don't feel like me talking would provide anything productive to the situation at that time.
However, if there is something that needs to be learned in that particular lesson, I find that in most cases the "right" or needed teachable moment presents itself.
It seems to boil down to two different possibilities :
1. They need more practice on their own
2. They need my (a teacher's) help with something specific
Because I see my primary job as helping the student to become aware-- of what they are doing (what's working, what's not), what is the process necessary to achieve certain goals (short term, medium term and long term), what is needed to help further progress, etc-- I will be alert to use any circumstance as an opportunity for them to become more aware. So if it is a matter of them simply needing more time with the piece, we will talk a little about what that means. They learn about the process.
If I am not sure how much to say, or exactly which points will be the most helpful in those moments, I will firstly ask them how they feel and if they have any questions about the piece. Sometimes they do, sometimes they don't.
With some students, they are not achieving something as well as they can because they are still learning the technique. So I will focus on a specific spot and on a specific technique needed to achieve this section of the music. Talking is not always needed for this kind of work. And in most cases with this kind of work, it is about them learning how to discipline enough to break down the section even further than what they have been already.
Sometimes I will not say much at all and we will just simply move on to something else.
What I do depends on :
1. Where I sense the individual to be emotionally, mentally, physically.
2. What I feel is needed
In that order. I try to be very sensitive to whether or not they can take a lesson on a certian point or not. So ultimately, my reaction to their efforts depends largely on their state of being.
With some, especially adults, it is simply a matter of being human. So there can be personal and impersonal issues to deal with as well, to which I am willing to help with in whatever way I can.
m1469