The gravest mistakes entrepreneurs make, young and old, aren’t in thinking about strategy or hustling on day-to-day tactics. They’re in the fundamentals of the people, problems, and solutions — and worse yet, in assuming they’ve got these fundamentals nailed.

How do I know? I made all of these mistakes in a very big way — all before turning 22. But when the rocket fuel of venture capital finally made for an extravagant explosion for my company in May of 2014, I learned some unforgettable lessons that I’ll be taking with me to my next venture:

A founder must have a team of people that share the same personal goals.
While the vision of the business should already be core to the founding team, it’s important that you and your cofounders realize achieving this vision comes with countless implications to your personal lives. You should bear the burdens equally, which will probably include small salaries, long work hours, shifting responsibilities and uncertainty. The team must be able to agree on not just the growth path of the company, but the personal growth needs of the staff.

Beware if a teammate demands you raise money to pay salaries — or worse yet, relocation costs. Fundraising is a huge decision for the startup and its employees, and personal demands like these are a clear indicator that your teammate is putting his needs ahead of both the business and his cofounders.

See also: The avoidable mistake every entrepreneur makes

A founder must be solving a valuable problem that the team cares about and understands.
The classic story of the skilled hacker who builds the next must-have app to solve his own problem isn’t always realistic. If your real-world team isn’t comprised entirely of your target customers, you should all at least have a deep understanding for the problem you’re solving and the user who most consistently experiences it. Then, once you’ve set your eyes on an interesting challenge, make sure it’s valuable. Find a way to collect money for solving the problem before you build anything, even if it means cooking and delivering those on-demand Paleo snacks yourself. Your drone budget will come later.

Beware if your team starts gravitating toward a shiny business pivot that you poorly understand — or worse yet, just can’t be convinced to care about. At the worst, it might lead you to spend months building a beautiful, fully-functional app or website that never goes anywhere. Why? Since you didn’t understand the problem fully, you didn’t build to solve a valuable problem — you just made something “nice to have.” If the story of the Everest app is any indication, nice-to-have products rarely survive, even with great design and eager investors.

A founder’s business must be able to execute on an effective solution.
Your team is your tribe and you’ve got your eye on a valuable problem, but you have no idea what to build or how to do it. While this is the shortest of these three walls to smash into, many young founders will still be unprepared. Getting out of a rut like this demands decisive action — including firing and recruiting — to which few young entrepreneurs are exposed.

Beware if you can see the right problem and have a validated, valuable idea for a solution — yet your team can’t build it. If no one is willing to learn to make it happen, find a different problem or a different team, but don’t get stuck. Getting stuck destroys startups.

Learn and laugh from these lessons, but try not to repeat them — whatever your age. None of us have time to waste on the wrong partners, problems or misguided solutions. There’s just too much to do.

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Michael Gasiorek is an entrepreneur, digital nomad and effective altruist. After time in diplomacy, corporate advertising, and publishing, he now grows the Startup Grind story and community as editor-in-chief. His focus is on the people and technologies improving human effectiveness and reducing suffering.