I am now, have been and will be wrong

With Markets, look at your real customer base, not the people who "could" use your service. The ones who WILL use your service. If the market isn't large enough, (big enough to matter) reevaluate the time/money/effort it will take you to succeed. If you are willing to sacrifice the resources in order to say "I did it." That's one thing, but recognize this is no longer a true business, but a hobby.

How will you know if your market is large enough? Ask, figure out the need you're servicing. How badly they need to change, what is going on to accelerate the change, and who is going to make the change first.

Don't make the solution first, and then search for a problem, only to realize the market's so small that it doesn't matter to anyone else but you.