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
From hands to machines It has rarely proved practical to produce exactly the same product by machines as we produced by hand. Mechanization requires you produce an equivalent product, not identically the same one. Richard Hamming, The Art of Doing Science and Engineering: Learning to Learn The Nature and Art of WorkmanshipThe Real World of Technology