You go to work. You sit at a desk all day. You type, and write, and process, and whatever until your brain turns to mush.
That's most of you, at least. But some people, some people I know, aren't quite resigned to just do their 9-to-5 half-assed and half-asleep. They go that extra mile. The bring home that 97%-fat-free-tastes-as-good-as-the-real-thing-reduced-fat-turkey-bacon-that-nobody-can-afford. And yet, there is a danger to being good at your job. Many, in fact. Most of these, however, lead to you inevitably being fired. That may not be the case in all situations, but usually... your ass is proverbial grass when you're too good at your job.
You've seen them. Those little people you had to step on to get where you are now. It wasn't that hard to step on them, though, as they were usually tripping over their own feet anyway. Unfortunately, you're now the guy who they look to to pick them up off the ground and put them on their way.
This is not nearly as rewarding as it seems.
You see, people, on the whole, when a problem is solved for them tend to reproduce the problem. This makes more work for you. And since you're "the best one they've got", you end up being the fire extinguisher for every single fire out there, from a match to a raging inferno. I hope you brought some sunscreen, because being too good at your job is going to get you burned.
This one is fairly self-evident. When you're good at something, people tend to give you more work, on the idea that you can do it faster and better than someone else who could do it. Unfortunately, most people don't seem to understand that you can either have faster, or you can have better. Do you want it done well, or do you want it done now? is a good example of that. Then, of course, they get angry when it's not done on time, ignoring how they've given you the workload of 20.
Never be smarter than your boss. And if you are, hide it. There's a little thing about job security that people like to have, and by the dilbert principle, those who are promoted way above their stations are constantly nervous about being usurped about someone more intelligent or skilled. You show these traits by being good at your job.
Remember, this person has the ability to fire you.
Really, see the above section about this. If your boss fears you, no way he's putting you on his level. He'll fire you way before you get that chance, or worse, get promoted above him. That scares him shitless, and well, you're the one to get shat on.
Someone came up to me and asked what the best way to keep your job, get promoted, and generally get fat rich off of stock options is. I gave them one piece of advice. Always, always remember:
Never be too good at your job. | 
