Even when I’m traveling, I try to get in some sort of Jiu Jitsu practice. When I was in New York a few weeks ago, I took two lessons from Paul Schreiner, one of Marcelo Garcia’s instructors and a great student of the game.

A lesson with Paul is not cheap. It costs as much as three months’ worth of group lessons at your local grappling school. But if you are up for learning, you will have spent your money wisely.

Paul taught me lots of good technique and strategies. But what I came away with are two mistakes I’ve been making more or less consistently for the past 20 years.

These are very basic mistakes. The sort of thing I should have corrected before I got my blue belt. That I’ve been able to perform as well as I have all these years is a miracle. I’ve obviously developed some unconscious compensating movements – but I’ve no doubt that I will be considerably better once I actually correct the mistakes.

I had the same experience when I used to write advertising copy. I’d write a sales letter or space ad that I felt proud of and then test it – only to discover that it didn’t work at all. Analyzing the dismal results, I could see the mistake immediately. It was usually some fundamental rule I broke in writing the headline or the lead.

The same holds true for my personal relationships. Looking back on conversations that went south, I can usually spot a freshman communications error: failing to acknowledge the other person’s perspective or, worse, denigrating it in some way.

It would be interesting to create a series of basic rules for every endeavor – a list of things one knows but often forgets. Let’s see… what would that be for entrepreneurial ventures?

20 Very Basic Business Mistakes That Will Kill Your Start-Up Idea 

1. Starting a business to serve a market need that doesn’t exist
2. Spending good money and time making the product before testing the idea
3. Believing that your great idea is worth a lot of money.
4. Believing that the market is wrong when it doesn’t like your idea rather than understanding that there is something wrong with your idea
5. Believing that being first to the market is the most important thing
6. Hiring MBAs from Harvard and Wharton
7. Spending money and time protecting your idea before proving the concept
8. Spending money and time perfecting your product before proving that it can sell
9. Spending time and money on anything irrelevant to market-testing your idea, such as renting an office, printing business cards, etc.
10. Underpricing your product
11. Overpricing your product
12. Going into retail
13. Having a business plan that’s based on general advertising
14. Having a business plan that’s based on raising millions
15. Having a business plan whose ultimate goal is exiting for big cash
16. Not paying attention to someone in the industry that takes the time to explain to you why your idea can’t work
17. Not moving forward with your idea simply because some expert said it can’t work
18. Believing you have to start with a “vision”
19. Believing that your business has to “touch” a million people
20. Thinking you can hire marketing and sales talent if you don’t have it yourself

It took me about 10 minutes to jot down the above list, but it took 40+ years to fully understand it. I’m tempted to say that if I’d had it when I was young, I’d have arrived at success much sooner and enjoyed much more of it.

It’s unlikely that I’ll be starting any new businesses any time soon. (I’ve promised K I wouldn’t.) But this list might be helpful to you or someone you know.