In the classic sci-fi spoof “Men in Black,” Agent K (Tommy Lee Jones) tells NYC police Detective James Edwards (Will Smith), who discovered a space alien living on Earth: “Fifteen hundred years ago, everybody knew the Earth was the center of the universe. Five hundred years ago, everybody knew the Earth was flat, and fifteen minutes ago, you knew that humans were alone on this planet. Imagine what you’ll know tomorrow.”

Along those same lines, I’ve read that the early 20th Century humorist Will Rogers once said, “It’s not the things we don’t know that get us into trouble, it’s the things we know that ain’t so.”

(Related: Set Up to Fail: Bosses Create Problem Employees More Often Than You Think)

Now, I’m not an alien hunter or a humorist, but in my work with independent advisory firm owners, I have found Rogers’ words to be surprisingly true. Of course, we’ve all had tightly held beliefs or ideas that we’ve found to be not quite as “right” as we thought. Sometimes they can really mess up our lives, but when we own a business, our strongly held ideas can cause real problems. To succeed, it’s essential that we know what we don’t know.

As I’ve written before, every advisory firm is a work in progress. That progress comes from learning, primarily through trial and error. That’s because every firm is different. The owners are different, the employees are different and the clients are different.

While we business consultants have seen many things that worked and many that didn’t, we never really know what will work in a particular firm, and neither do the owners. To successfully run and grow an advisory firm, it’s essential that the owners know what they know and what they don’t know — and take steps to learn what they need to know.

Of course, it’s human nature to pretend we know things that we don’t, partly out of ego and partly out of insecurity. But either way, when a business leader does it, it can be harmful or even fatal for their business.

To run a successful business, owners need to be realistic about themselves. Everyone has doubts and insecurities about their business and their career. The most successful firm owners I know face the things they are insecure about so they can get past them to make sound business decisions.

To help business owners do that, I get them to understand that it’s OK to have fears and doubts, and to not know everything. What isn’t OK is to let those things get in the way of making sound business decisions. Admitting our fears frees us up to decide if what we’re afraid of is truly worth being afraid of — and if it is, to come up with a strategy to prevent it from happening.

When we admit what we don’t know, it frees us up to learn more about it. As I said, building a successful advisory firm is mostly trial and error. That means trying what seems to be the most reasonable course of action (hiring someone, adding a new service, launching a marketing plan, etc.), then, learning what you can from the results — both successes and failures should teach you something new — and deciding what the next reasonable step should be.

Humans are also tribal animals. We work best in teams, so it’s also important to ask other people for help. (In fact, some of the most successful owner-advisors that I know ask their employees for help even when they don’t need it.) Other people can bring more experience or judgment to the table. I’ve found that firms that involve more employees in their project are usually more successful, particularly when the firm owner is a good role model for trying new things and learning from failure.

“Other people” can and should include people beyond your employees. Strategic partners and even clients can be valuable participants in learning from new projects because they provide different knowledge bases and perspectives.

Fears and failures are only bad things if you let them prevent you from ultimately achieving the level of success that you want. To get started, accept what you don’t know — especially what might happen and how it will work out. Often, you’ll realize that you did know all along: you just needed some time and some help to figure it out.