It is natural to want to employ your friends in times of need. The world is a harsh place and your friends soften the harshness, besides you know them. The problem is that yoi often donot know your friends as well as you imagine, friends cover up their unpleasant qualities so as to not offend. Since honesty rarely strengthen friendship you may never know how a friend truly feels.
Your enemies on the other hand, are an untapped gold mine that you must learn to exploit. An enemy unlike a friend expects nothing because he has more to prove and nothing to lose. An enemy at our heel strengthens our wits, keeping us focused and alert.