I'm facing the same experience. I see how it's exhausting and depressive the feel of "failure". I quit my first job trying to clone some successful idea to run it in my country with no background in marketing or business. I was driven by dreams and hoped to be independent but there was no business vision. After two years, i returned to work with other companies, but i continue to work in side projects. I think the worst error that we made is the pursuit of "perfection", trying to do what big sass companies does with hundred of engineers. Big companies fail and fail a lot but they can surpass that by other resources. To summarize, i think the lean startup is the basic of any business (in software and all other business fields), it consists on building an "ugly" solution ( for a real problem) first than sell it and than continue till perfection. We can learn a lot from yahoo and nokia ...