Designer, implementor, user, writer A Fragment by Donald Knuth dl.acm.org Thus, I came to the conclusion that the designer of a new system must not only be the implementor and the first large-scale user; the designer should also write the first user manual. The separation of any of these four components would have hurt TeX significantly. If I had not participated fully in all these activities, literally hundreds of improvements would never have been made, because I would never have thought of them or perceived why they were important. Eating your own dog food making
Haven't you noticed? I remember my mother sitting me down at the age of about five with pencil and paper to draw an acacia tree in the yard while she busied herself with her own sketchbook. After a while she came over to see my efforts. “Splendid! But haven’t you noticed how the trunk narrows as it rises? And see how the branches flatten out sideways, not like that oleander over there, where they all go up at a steep angle. Now don’t rub that one out, just do another drawing to compare with the first one.” Jonathan Kingdon, In the Eye of the Beholder Looking Closely is Everything seeing