The first customer is not the hard part
Why the first one is easier than people think
Your first customer is usually someone who already knows you. A friend, a relative, someone from church, a former colleague. They are not buying because your offer is compelling. They are buying because they want you to succeed.
That is not a criticism. Take the money. But do not mistake it for proof that the thing works.
What the first customer does not tell you
It does not tell you whether a stranger would pay. It does not tell you whether the price is right, because someone who likes you will pay a price that a stranger would refuse. It does not tell you whether you can find more of them, because you did not really find this one.
I spent two months after my first sale believing I had solved the hard problem. I had not started on it.
Where it actually gets difficult
The second customer, if they come from the same circle, teaches you nothing new. The first one who does not know you is the real test, and that one is much harder to get. You have no goodwill to spend. Everything has to stand on its own.
That is when you find out whether the thing you are selling makes sense to somebody who has no reason to be kind to you.
What to do about it
Sell to a stranger as early as you can, even if it is uncomfortable and even if the sale is smaller. The information is worth more than the money.
And when you count your customers, count the ones who found you separately from the ones who already knew you. The second number is the one that tells you whether you have a business or a favour.