One of my favorite things about my job as a CEO is that I get to help people build careers. However, sometimes this means I have to give advice no one wants to hear – things like, “Don’t waste a year or two in a job that’s going nowhere because it could ultimately make the difference between becoming CEO/CIO or staying at VP.”

The fact is, no one’s career progression is as long as they think it is. You may have a 40-year career, but the steep curve of progression at the beginning will gradually flatten. It’s not linear, and you may be at essentially the same level for ~ 20 years. This means you really only have 15-18 years to get to the C suite – 20 at the most. If a seat in the C suite is your goal, you can’t make mistakes. So, what mistakes do you need to avoid?

Here are the six I see most often.

Mistake #1: Following the same boss more than twice. Why? You need to understand the difference between being dragged along and labeled as his or her “guy,” and being responsible for your own successes. Your first boss is the one who will give you the first big promotion, but if you follow her to the next company, he or she may be focused more on their success in the new role and less focused on you and your growth. In most companies you are worth more to somebody else than you are in your current role. By the time you’ve followed a manager for a third time in a row it becomes hard to hide.

The same idea holds true for managers. I generally won’t let people who have a lot of career velocity follow me more than once. Don’t feel compelled to bring your most productive and agreeable people along for every ride with you. If you bring a team to each of your new gigs, you lose the opportunity to build a new culture. (For reference, read Tony Hsieh’s “Discovering Happiness.”)

Mistake #2: Not working in at least two sectors in your industry. In his book “Linchpin,” Seth Godin makes the point that “linchpins” are the essential building blocks of great organizations. What’s a linchpin? It’s a person who holds at least part of an operation together. These are the folks who are indispensable, even if they’re not super well known in their industry. In today’s workplace, they get the best jobs and have the most freedom. However, it’s hard to be a linchpin, a connector, if you’re only good at one thing. As Godin writes, our economy historically depended on people being compliant — cogs in a giant machine. But those cogs in aren’t rewarded anymore. They’re increasingly replaced, often by machines. What happened to all those folks who were really good at selling software, right up until the cloud came along? What about the people who were the best at retail distribution, until Amazon? If you used to sell automotive navigation systems, your specialty is now a feature. No matter what industry you’re in, at some point the total addressable market will shrink and you’ll be in trouble. The goal is never to be segment limited. If you’ve had experience in a couple of sectors you’re less likely to be sidelined.

Mistake #3: Not working for (at least) two companies. There is nothing wrong with attempting to rise through the ranks at a big company. Yes, you will see many CEOs at today’s Fortune 500 who rose up in GE or Proctor & Gamble, but this is increasingly rare. Most of your career growth happens between the ages of 23 and 37. My advice: be strategic about the first company you work for. Pick the right industry first; focus on high-growth sectors and look at the market leaders’ gross margins. Identifying the companies making money and going after them is how you’ll have rapid progression and make enough money early in your career. Manufacturing and oil & gas, for example, are growing slowly. You won’t get early career velocity there. When you’ve found your first company, stay for three years, learn as much as you can, learn how to be managed, and then move on. When I’m looking at new hires, I want to see a title change if they’ve been with the same company for a couple of years. That tells me someone had the sense to promote that person, and odds are I will, too. When someone who’s working for me tells me they’ve found a better opportunity, I say, “God bless you and good luck.” The chances are, I will look to rehire that person at some point because they had the good sense to move on and grow.

Mistake #4: Not being great in (at least) two disciplines. This might sound controversial but being really good at two things is more valuable than being great at one. If you’re in sales and marketing, you should be well-versed in finance. For example, if you’re a physician who also understands technology, I’m betting you’re going to have opportunities you might never have dreamed of while in medical school. Bottom line: In today’s economy it’s very difficult to advance if you’re only focused on one area of expertise. You need to show employers you’re adaptable. This is also in line with the linchpin idea – if you’re the connector between two departments, you’re more valuable. I’ve observed that companies seldom scale if the CEO is really technically adept but doesn’t have another skill set, like sales. A marketer needs budgeting skills. An R&D person needs to understand sales. Being good at one thing may be a benefit early in your career; after that it’s about balance and not having blind spots. As you progress in your career, having multiple skill sets becomes more important.

Mistake #5: Not living in (at least) two cities. What are the statistical odds of the next best opportunity in your career being only 50 miles away? Almost zero. I counsel young people all the time to get out of the region where they grew up, unless it happens to be within 50 miles of New York, Chicago, Boston, or San Francisco. There is really zero chance your next best opportunity is going to be in Portland, Maine, Tampa or Salt Lake City. While those may be fantastic cities to live in, if you’re looking for career opportunities, you have to put yourself in the right geographic area. When I’m looking at new hires, I want to see evidence that they’re adaptable and willing to take a chance. If it helps you narrow down your options, look for cities where a few million people live within two hours’ drive.

Mistake #6: Not living in two countries. The United States accounts for about 24 percent of global GDP according to YCharts. If you look at International Monetary Fund numbers for GDP by PPP – purchasing power parity – it’s even lower – 15.4%. That means other countries account for the vast majority of GDP – more than 70%. Every potential C-level executive could benefit from spending at least two years in a major market outside the United States. This is unbelievably important. If I’m looking at two virtually identical candidates and one has lived abroad, and the other hasn’t, I will always choose the one who has lived outside the U.S. I think of Canada, Australia and the United Kingdom as the 51, 52 and 53rd states in the U.S. Until you have lived in Europe, you don’t understand medicine and social welfare. Until you’ve lived in another country, you can’t see that much of the world thinks the number of hours Americans work is crazy. And this is sort of an aside, but people who can speak other languages add so much value to any organization, especially in our increasingly connected world.

Some of these mistakes are easy to make, but they’re also relatively easy to avoid if you’re thinking ahead. Losing even one year of progression early in your career can put you out of the running for the C suite. If you feel stuck at a job or frustrated, don’t wait for someone to save you, and don’t say you’re worth more. Ask for broader shoulders and more responsibility. Yes, luck is involved in having a great career, but ultimately, it’s your job to manage your progression to the C suite. Do great work, be focused, and don’t be afraid to raise your hand when someone gives you a challenge.