Lewis knew that a high-pressured workplace was the price for a six-figure payday. The Berlin-based, entry-level consultant believed the stress was worth it for the fast-track to a €150,000 ($162,170; £128,460) base salary at one of the world's most prestigious firms.

"There has to be a willingness to be chained to the desk. You accept those conditions in return for such a high salary – that's the game. If you're not working 12 hours straight, the response is 'you're being paid this much, so you have to'," he says. "When you earn such a high wage it's a psychological block – you feel you've earned it, and worked really hard to get there. You want to get out, but how much of a salary cut can you take?" READ MORE