Every week I talk to aspiring founders seeking validation for their ideas. They're ambitious and optimistic—but often dangerously wrong about how to succeed.

The worst startup mistakes are those countless others have already made. As a founder, I find myself urgently saying "Stop! Don't do that!" to new entrepreneurs headed for predictable (and avoidable!) pain.

Look, you'll make your own mistakes. But most startup wisdom comes from getting slapped in the face repeatedly until you realize you can choose a different path.

Here are 10 fundamental ways I've screwed up and figured things out over six years building companies. You might not listen (most don't), but these insights could save you time, pain, and maybe even your company.

1. Don't bring on a cofounder (find a founding team instead)

I waited to start Almanac until I had cofounders because I didn't want to face the dark early days alone. But in 9 out of 10 cases, cofounder relationships fail.

They create an illusion of equality where all decisions need consensus, slowing everything down. They bring unnecessary emotional complexity into an already taxing journey. And ultimately, one of you will likely be a better fit for the startup marathon than others.

The most successful founders I know incorporate alone but bring on a founding team they compensate generously with equity while retaining decision-making power. This approach preserves speed and, frankly, these founders end up wealthier because they own more of their companies.

2. Don't fundraise (or raise more than you need)

Many founders think fundraising is a primary requirement of building a company. It's not. The only true requirement is building something people want.

Investors aren't your customers. Their approval means nothing. And their money isn't free—the more you raise, the more you dilute your ownership and the bigger you have to grow to justify your valuation.

The best founders validate their market and create customer traction before raising significant capital. The more you can show by the time you need to raise, the higher your valuation and the less you'll dilute yourself.

Remember: the goal is to make money, not take money.

3. Don't build before validating your market

It's relatively easy to code almost anything these days. The hard part is picking the right market.

Your real task is identifying a market with a significant underserved need that can grow into a multi-million dollar enterprise. You're like a prospector searching for minerals with basic tools—and setting up in the wrong place is incredibly difficult to correct.

Smart founders spend their early days talking to customers, not coding. They use landing pages, design prototypes, and human-driven pilots to confirm real demand before investing in building the actual product. Wait for the market to pull you into building.

4. Don't do it as a side project

I understand the impulse to start part-time until you're "really sure" while keeping income flowing. But I've never seen a founder successfully start a company on the side.

Finding the right market requires all your time, concentration, and energy. You won't feel real pressure to figure it out until your back is against the wall. There's no substitute for staring into the abyss of failure to get practical and quick.

Be smart—have 12-18 months of savings and confidence you could get a job if you fail. But make the leap. Starting a company is a full-time commitment.

5. Don't get stuck on your idea

Most founders think their job is to bring their brilliant idea to the world like a prophet. This is backwards. You're not an artist creating something you want.

Your job is building something other people want, validated by whether they pay for it. Even if inspired by your experiences, you are not your customer. What your market really needs will surprise you.

The best founders are motivated by one metric: how much customers pay for what they've built. This orientation makes it easy to pivot and evolve, even if the end product isn't what they initially envisioned.

6. Don't target a large market

Counterintuitively, bigger markets are often red oceans—well-known and well-served by established competitors. As a new company, you won't have time or money to match their products before running out of runway.

You need a market that looks unattractive from the outside but can be captured with a product significantly better than alternatives. These markets are, without exception, very narrow.

Narrow markets create winning startups because they have fewer, more specific requirements, making it easier to build something great. Target messaging is clearer, and acquisition is more efficient.

Start narrow, get traction, then expand.

7. Don't wait to launch

Many founders fear launching, thinking their product isn't ready or that beta feedback is sufficient. The only way to truly know if people want your product is to launch it publicly to a statistically significant group.

If many try it and stay (even while complaining), you're onto something. If nobody tries it or users quickly churn, that's a sign to pivot.

Beta customers help refine your product but don't prove you have a market. Launching answers the critical question: "Do people really want this?" Success creates momentum; failure creates learning. The only way to lose is not launching.

8. Don't get distracted by non-essentials

As an early-stage founder, kneecapping yourself with an office in an expensive city and local hires burns through limited funds quickly.

Efficient founders hire great people wherever they are, saving money by not paying Silicon Valley rates. They build asynchronous cultures where people spend time building or selling, not sitting in meetings.

Being distributed forces you to document processes and communicate clearly—habits that compound as you scale.

9. Don't forget your why

I promise you'll encounter difficulty beyond your wildest imagination. Team members will leave. Deals will fall through. Customers will churn. Vendors will fail you. People will disappoint you.

The most resilient founders stay focused on their mission: survive, make money, thrive.

To endure the pain, remember your why. Success isn't everything going right—it's progressing toward your goal. As long as your key metrics trend up and to the right, you're moving forward.

10. Don't give up

Before product-market fit, your most precious currency isn't revenue; it's motivation.

Every founder—every single one—hits points where continuing feels impossible. The secret is that those who succeed simply keep going, one foot in front of the other, eyes open to the learning along the way.

It takes years to become an overnight success. Most of those years involve failure and pain. But if you don't give up, you won't fail. And because of the compounding nature of startups, persistence almost always leads to enormous financial returns.

So don't give up. And if you need founder-to-founder advice, I'm here to help.