I got over a dip - about 10 minutes ago. For the last 2 months I had what seemed like an unsurmountable technical problem. Well, it was surmountable but I really didn't believe in the business enough to go through all the steps to fix the problem. Well after an expresso this morning I just solved it and now I feel like I can take on the world - I don't really care if the business idea is that good anymore because, by fixing this problem, I feel I have something valuable.

If you've been working on something for 6 years you've definitely got something valuable. I recommend that you don't quit.