There's a nice Yugopnik video about a "capitalism survival guide" that tries to help navigate a disillusioned worker in the modern hellscape. There are some two VERY important things that he brough up as tips to the modern worker:
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Everyone is winging it. Regardless of the high expectations you see in job descriptions, you need to figure out how to bullshit your way past them: unless its something like a doctor, pilot, or engineer, you can probably learn the skills without getting a degree in them.
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Work JUST enough, the employee that stays the extra hours and stuff doesn't always get the promotion. Depending on your work and position, working more might just be a net negative, as your extra mile becomes next time's bare minimum. This can then hurt your co-workers too, and as for you individually, you might suffer the curse of being the "go-to" guy. Ergo, extra work for you for the same pay as before.
Don't undersell yourself. Remove phrases like "oh, it was nothing" from your vocabulary in the workplace. You should still be nice and gracious and stuff, but always be willing to accept credit and praise others direct at you, and never undersell your own achievements out of some misplaced sense of modesty.