Focus on sales, even if the product doesn't exist yet.

Do you enjoy selling this product?

Do you understand who the market is?

Do people want to buy it?

Do they want to buy it even if you haven't created it yet?

Will they give you money for it now even if it won't be ready for a few months?

Set some targets for yourself. For example, commit to calling at least 100 prospective customers and trying to sell the product before you give up on the idea, and don't move forward until at least 6 people have agreed to buy it (or paid in advance).