I don't have experience stick fighting, but I am an amatuer kickboxer(about 16 amatuer fights - kickboxing/muay thai).
I'm sure that the experience is pretty much the same, so here is what I think. Thinking of your opponent as the enemy isn't necessary, or good. It often makes you tense up, and makes for a bad sparring partner. When you spar, you are not there to kill your opponent - You are there to work with eachother.
I thought the same way as you did when I first started kickboxing. However, many Friday nights spent sparring in the ring, allowed me to get experience, and be able to calm down.
You don't need to think the guy is going to kill you to be able to compete. You need to practice and be in shape. I think the key ingredients to fighting in any sport are stamina, heart, and skill. You need all three of those put together.
I don't care how much you hate you opponent, or think he is going to kill you, if your in the third round of a fight and your so tired you can't lift your arms or throw a kick, your going to get knocked out.
Also, no matter how hard and intense you spar in the ring, it will never compare to an actual ring fight or street fight.
Hope this helps.
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- Sandon