I had my Global Entry interview last fall, and my experience was slightly more eventful than most applicants'. By the "luck" of the draw, I was assigned to a notoriously long-winded officer, so my interview took longer than that of anyone else in my group. First, he seemed to have trouble getting the system to confirm my address, and ended up using a less specific version of it. The actual interview was fine, if drawn out by chitchat. At the end, after telling me that I would be approved, he delivered a lecture on the many do's and don'ts of crossing the U.S.-Canada border by car, with stern warnings about what would happen if I did anything wrong. He then shared helpful tips on obtaining Global Entry for one's minor children after getting it for oneself. I wanted to stay on his good side, so I let him go on and on with all this unsolicited advice and didn't bother telling him that I don't drive and don't have children. I suspect it wouldn't have made any difference if I had. :)
The interview was also drawn out by the difficulty of getting a set of readable fingerprints. My hands were dry; in retrospect, I probably should have prepped by moisturizing. After about five attempts, we finally got a set of prints that satisfied the officer and the machine.
This is all to say that even an interview that hits a few bumps is not all that bad or stressful, and it's nothing to worry about. Don't lose any sleep over it!