1) your enemy often has a clear insight into an area of development in your personal or professional life and more than a willingness to share this insight with you. A friend may offer advice to maintain the status quo rather than tell you something honestly about an area of development opportunity that may jeopardize your friendship.
2) Your enemy can teach you the important lesson of patience. The best blessings come with time and through devotion.
3) enemies teach us the invaluable lesson of respond rather than react. Easier said than done, I know, but no better practice for longevity, awareness and equanimity.
4) Enemies provide an impetus for change.
5) Adversaries are often a reflection of our shadow nature. We have adversaries in the external world because our inner world is in conflict. Loving your enemy or adversary is often a very good way to overcome differences and find a satisfactory solution.