If you are not talking about "missing market or lack of customer acceptance" I am assuming you haven't gotten one of your products in the hands of your end customer.

I would suggest building a very simple feature set that you an launch quickly (MVP in startup terms) or even a quick mockup and ask your end customer (or who you think your customer is) what they think of it.

If you have a prototype a customer wants then you will be excited. Set some deadlines, targets, goals, and really execute on it.

That's my 2 cents.