It's not the guy who sneaks around reading other people's mail trying to angle hisself a leg up that's going to grab the brass ring. That guy doesn't cooperate so even if he appears to be the best worker, his boss will be like, "Well, you clearly know how to get the job done and you're willing to cross those lines that other people won't cross in order to excel. But here at this building, we value cooperation. And you can't spell cooperation without two O's right next to each other, just like the two eyes on my face which I can use to clearly see that you read other people's mail! I''m sorry, but the end does not justify the means. If you're opening letters that aren't addressed to you just to get ahead, who's to say tomorrow you won't kill me?"
Happy Cooperation Day! Be a good worker.