Someone said there's only one plot in fiction: "Who am I?"

The drama unfolds when the protagonist takes new actions to meet new challenges, but in doing so changes so much that he ultimately betrays himself and fails, until he rediscovers his roots, and with them his purpose, his strength, himself.

It is not only true for fiction. It is true for life. It is true for business. If things are good, you are now running a business that is starting to get traction and make its mark on the world. If things are really good, you have now achieved a success and scale that mean you are ready to take on the big guys.

This is when it gets tricky: Right about now, someone will be telling you that competing in the top league requires throwing away the old playbook and start playing a completely different game; that the people and culture that took you from zero to small to medium will not be enough to make you big, and that it's time to learn from the grown-ups. It's tempting to fall for this line of thinking: There are consultants, industry specialists and management gurus that make a living out of it, and have a pocket full of best practices, benchmarks and manuals to hit you with.

While there is a lot that you have to readdress as you are getting ready to scale, from your supply chain to your sales, now more than ever is the time to hold on to who you are and what made you grow in the first place. After all, incumbents are not successful because they're big, they're big because they were once successful.

If anything, we have lost track of how many senior managers privately complain that their organisations have gotten dumber as they have gotten bigger, becoming more conservative, second-guessing every decision and favouring process over product. In their words, this is easily the largest threat to their existence.

There are three common mistakes in particular that you should avoid at all cost.

Best practices, or the art of marketing solutions to someone else's problem

Tony Hsieh is the CEO of Zappos, an online shoe retailer that he took from zero to US$1 billion in less than 10 years, before selling it to Amazon. He did it by intentionally going against the conventional wisdom of e-commerce in order to gain a competitive advantage: Where other e-shops were forcing their customer-care employees to handle calls as quickly as possible and not paying them if the conversation lasted longer than a few minutes, Zappos service agents were invited to spend as long as they liked on the phone, share personal details and make people happy even if it meant sending them to a competitor, knowing that in the long run "wow your customer" is the most beneficial strategy for a retailer.

This is what Mr Hsieh thinks of competitive benchmarking: "Following best practices is a great way to stifle innovation and ensure that your business is average and behind the times."

Best practices are really a double jeopardy: First, they have been originated for a specific company with its own culture, products and processes, and adopting them means borrowing the solution to a problem that is not yours; second, virtually any policy that has been effective enough to become a best practice has since been incorporated by the market, and that may leave you in the same predicament as the generals who famously always fight the last war.

Slicing and dicing: the atomisation of responsibility

Vice-president of emerging media; chief evangelist; head of engagement; search marketing manager; paid media manager; chief innovation officer; head of partnership development; vice-president, new initiatives; director, always-on marketing.

This is just a brief selection of the modern job titles you can stumble upon on Linkedin. They're a direct consequence of the explosion of marketing channels, opportunities and practices that the digital age has brought along, and they've been created by reaction rather than by design.

Every time a new activity was considered worthy of enough time and money, a new position was created. This has resulted in a Kafkian bureaucratic nightmare: an army of specialists who are each responsible for something and accountable for nothing, fighting over limited resources to win their narrow battles, with no ownership or understanding of the bigger picture.

This has in turn produced fragmented initiatives that, under the pretence of 360° marketing, try to do too much of what doesn't necessarily matter: driving traffic to a corporate website, increasing likes on Facebook, growing brand awareness, recruiting new followers on Twitter becomes ends rather than means, because someone's annual target and career review is tied to each one of them. The one objective that really matters, be it about sales or average revenues per user, usually belongs to someone so far high up the food chain that it gets lost in this process of slicing and dicing.

It's the corporate equivalent of the orchestra focusing all their attention on hitting the right notes while the Titanic was sinking. Make sure that, as your ship grows bigger, you don't steer it along the same path.

"Keep it simple": how we've dumbed ourselves down

"For every complex problem there is a solution that is simple, neat and wrong."

This immutable law of human thinking, inspired by HL Mencken, is a perfect fit for business culture: As companies grow, we are tasked with changing a growing multitude of behaviours of a multitude of human beings across a multitude of contexts.

Yet, instead of acknowledging this complexity, we strip it down until we lose all human truth, and we're left with simple explanations and mechanics that make perfect sense on a Powerpoint slide, only to fail miserably once they step into the real world: "We can prove that we have x per cent more y than our competitor, why aren't people switching?"; "Consumers in focus groups asked for z, we gave it to them, and now they're not buying it"; "We set up an innovation fund, why are we not becoming more innovative?"

We deal with variations of these questions every day, and they all have one thing in common: They fail to recognise how, as human beings, our actions, our motivation and our feelings are contradictory and complicated.

For all the financial education you can impart on your children and spouses, all it takes is one irrelevant erotic picture of a woman to increase financial risk-taking in men; after decades of public service campaigns that provided a wealth of scientific data, the message that had the greatest impact on the drinking behaviour of young adults was a simple statistic showing that the majority of their peers drank less than people thought; charities have better luck asking lawyers to provide professional services completely for free than for a reduced fee. There's nothing simple about this.

As your company grows, you'll start dealing with greater human complexity: more and more diverse staff, customers, suppliers, influencers; at the same time, you'll be more removed from the field, because there will be just too many of them.

The worst way to manage the increased complexity would be to establish stripped down, "keep it simple" guidelines that everyone must follow no matter what; rather, hire talented people and make them accountable not just for the decision they take, but for the reasons that led them to it, and demand that the process includes information that you're not aware of. If now that you're bigger and busier you know as much as them, chances are you're both missing something important.

So how do you grow big without growing dumb? Just by being true to yourself, really. When your company was a small player, you didn't follow the industry's common sense. You probably defied conventions because there was something that you understood or made better than anyone else. Now that you are big, don't surrender to the temptation of doing what all the other big guys are doing. Hold on to your uncommon sense, instead. It is the one thing that you should never outgrow.