We have all seen it in our careers: people who we thought would have gone on to be the tops in their company or industry but who end up shooting themselves in the foot.
It could be a star sales executive, a top billing lawyer, or a rock star up-and-coming executive. When we first met them, we might have said that they were "scary smart."
Their intelligence is intimidating. They might have gone to an Ivy League college or a top 10 Business or Law School. They might have worked previously at the best of the best companies before coming to ours.
And yet their careers got suddenly derailed -- and always by their own actions.
We often asked ourselves: How could such a smart person do such a dumb thing?
And sometimes we might be looking at ourselves in the mirror when we ask the question.
So, here are the top 8 ways that smart people shoot themselves and their careers in the foot in the dumbest ways:
1. They assume their past success will continue in the future on new projects. There's an arrogance that can take hold in really smart people over time. They're used to being the stars. They're used to having an audience of admirers. Their whole lives have been a series of one success after another. Why wouldn't this pattern continue, they think? This over-confidence breeds lots of blind spots.
2. They stop paying attention to details. When you have success early in your career, you get promoted and you get further opportunities to show your skills. Quite often, you get more responsibility too. If you're over-confident that your past success will continue, you can stop paying attention to all the details like you used to during the early times when you had some of your biggest successes. You can start mailing in your efforts, or you simply delegate the details to others and forget to check up on them later. Because you're still so busy, you don't realize everything that's slipping through the cracks beneath you.
3. They forget their own strengths and weaknesses. Let's face it, none of us is perfect. No matter our college degree. No matter our LSAT score. No matter our latest promotion, we all have strengths and weaknesses. The most successful executives in the long-run never forget their weaknesses when they look in the mirror. They find a way to surround themselves with people who can cover those weaknesses because others have strengths in those areas. The smart folks who fail assume they can be experts in areas that they have no business offering opinions on.
4. They banish people from their inner circle who have a different opinion. Nobody likes to be told they're wrong. At the early stages of our careers, if our boss tells us we're wrong, we have to accept it. When we become the boss and someone tells us we're wrong, we can simply tell them they're probably not the best fit at our company or on our team. Over time, the smart people who make dumb mistakes surround themselves with "yes" men or women. They assume - based on all their past success - that they can't be wrong. And they will drive full-steam ahead on one of their decisions, even if it drives the whole company off a cliff.
5. They forget that you catch more flies with honey than with vinegar. There's an old saying: "be nice to the people on your way up, because you'll also be seeing them on your way down." There's a lot of truth in that. We all have highs and lows in a long career. At some point, no matter how successful you are in the moment, you will get knocked down by something or someone. And then you'll need allies and supporters. Therefore, don't alienate people by telling them how brilliant you are and stupid they are -- even if it never seems like you'll need their support in the future. You never really know who you might have to call on for a favor in the future.
6. They decide to move out of their area of expertise. Sometimes on business TV, you'll hear people quoting how so many big mergers or acquisitions have ended up destroying value instead of creating value. Remember AOL AOL +0% and Time Warner TWX +0%? Almost all of the big mergers that have ended up failing have involved a CEO of one company deciding that he or she is so successful that they are going to move into some new fast-growing area. Jill Barad took down Mattel MAT +0% when she decided that the toy business was too slow-going and they had to move into the fast-world of CD-ROMs by buying The Learning Company in the late 90s. It ended up writing off the $3.6 billion acquisition a year after making it. We might be successful because we know the business we're in but that doesn't mean we can now know every other business under the sun.
7. They don't build bridges with all the senior people who will have a say in their fate. A lot of times, smart people assume that their results will speak for themselves. But we live in a world where relationships matter. It's not just in Game of Thrones where good guys get their heads chopped off out of nowhere thanks to some enemy they never realized they had. That stuff happens every day in board rooms across America. It's again arrogance to think that your brilliance and successes will speak for themselves. They might have just the opposite effect of annoying some key influencers above you who think you're full of yourself and not ready for the next big promotion. You've always got to be selling yourself to others to ensure they know your success and abilities (although you have to do it in a way that doesn't annoy those above you). It's got to be sincere, not obsequious. Who's going to do your PR if not you?
8. They take needless risks in their personal lives. One final word of warning: if you think you can be the top of your game in your work life and have one vice in your personal life that won't affect it, you're probably very wrong. Whether it's gambling, alcohol, drugs, adultery, or something else, you're playing with fire if you can't control yourself in those areas. Sure the politicians like Anthony Weiner, Gary Hart and John Edwards come to mind, but there are lots of smart and successful executives, doctors, and lawyers who succumb to this one as well.
In conclusion, remember, nobody's bullet-proof. It doesn't matter how much success you've had in the past or what school you went to.
Remember the famous best-seller from the 90s by Andy Grove: Only The Paranoid Survive.
The smartest people who succeed in their careers for the long-term never stop working hard, never stop building relationships, and never lose touch with their own strengths and weaknesses. The day you start mailing it is is the day you can start packing up your things.
Not every decision we make in our careers will be right, but we better course-correct quickly if we make a bad one. If you learn that one thing, it's more valuable than a college degree from Harvard.
I'm a tech and media investor. I did a Ph.D. in Management at the Columbia University Graduate School of Business in New York, with a specialization in Strategic Management. You can follow me on Twitter @ericjackson, subscribe to me on Facebook, follow me on Sina Weibo, or Circle me on Google+.