Compartmentalizing by treating business as a “game” that honest people are simply playing poorly seems to be a place many start, if they want to be able to continue to see themselves as honest.
Once it’s just a game, and deception is part of it… why, you’re not even behaving unethically!
Empathy. Remove it. Don't necessarily steal willy nilly, but see people as pawns on a board to get you to the next stage of the game. You're not concerned with doing a good job, you're concerned with learning the players; their personality, their weaknesses, the power structure, etc.
Your goal is to move up the ladder and move quick. Get friendly with boss, the hold it over them. then get to the next step. maybe you need to pretend to fit in, maybe lie about qualifications. That's part of the board. Get powerful people to like you, get powerful tools and resources, and keep moving up.
Many stop around middle management since you start to need more money to push further, but it's a similar game as you go farther up, you just end up fighting against more players that may or may not be cleverer than yourself (and likely much more dishonest).
I think that's it really. You give up a great deal. Dishonest people don't realize how much they've given up. They surround themselves with equally dishonest people, and then wonder why they can't trust anyone.
