So, I've experienced this a couple times now. People who are in emotional distress sometimes come and talk to me about it.
For example, my good friend (ISFJ) just last night told me how his parents might be on the verge of splitting. I really love the fact he was willing to tell me this, but I felt kind of uncomfortable because I had no idea what to say. I asked some situational questions so I could better understand what he's going through, but him opening up to me generally put me into my "quietly-thinking mode" and I didn't say much. Overall I came out of the conversation feeling like I could have done so much more.
Am I simply over-thinking this? Is the fact that he was able to talk to me and "get if off his chest" enough?