Re: consumed by the opponent
IMHO, (Thanks, for explaining that to me, Seiser-san) The base emotions of fear and hatred are harmful and should always be avoided. I believe I've read in the Dalai Lama's book: The Essence of Buddhism that a main basis in Buddhism is the advancement of one's happiness through the complete elimination of these (and other) negative emotions.
Also, many of today's forward thinkers, like Deepak Chopra, MD, Dr. David Hawkins and Wayne Dyer, PhD have discourses on the physical harm one causes themself through the downward spiral of an emotionally depressing mental condition.
Long story short: Fearing, and especially hating others inevitably hurts you and rarely hurts the object of your ill feelings. The cause of an obsession like the one Miranda-san described above must be strong feelings of inability to handle an interaction with his nemisis.
Again, IMHO, the way to 'get over it' is to practice Aikido. Confidence in one's ability to defend one's self physically means all can be well, even in the worst resort. Mentally, give your convictions a workout- when you know you're right, your mind will provide you with ceaseless proof.
Miranda-san, within you is the ability to handle this guy. When you start to believe it, you'll be able to quit worrying about it and be happy!