Secret Sauce: Is this fun for me?
I started several companies because I thought they would make money - and they all failed. Then I started a company because I thought it would be fun for ME, and it worked.
I worked on this thing for 5-6 years. If it wasn't fun for me, I'm not sure I could have done it.
Ask both "Can I do this?" and "Do I want to do this?" And, will the answer be the same in 4 years?