It may seem odd to focus as much on the participant’s feelings as on the surface of what they say, but to put it baldly, feelings affect productivity. Feelings are important for other reasons too, but even confining ourselves to purely utilitarian grounds, we may note that unhappy people write worse software, and less of it. Given the restricted nature of most electronic media, though, there will often be no overt clue as to how a person is feeling. You will have to make an educated guess based on a) how most people would feel in that situation, and b) what you know of this particular person from past interactions.
— Karl Fogel, Producing Open Source Software