As I mentioned before in other posts here, I have already had my own businesses, which failed and I always felt that part of this failure was precisely linked to the fact of not being able to sell the products and services I was offering.

The growth of a business is tied to it's revenue. You have to be a good sales person. You are to first of all sell yourself to your customers before your product.
Your customers should have the best service during the purchasing process.
Developing your negotiating skill is also fundamental.
I am sure you will do well in your next business.
I also like the fact that you read for self improvement no matter the past failure.