Assuming that you are going after a big hill - I think you need to figure out the following things:
1. Is it a big hill after all - your customers might want something else. If it is not a big hill then figure out what a big hill is and reorient-realign-refactor.
2. If 1.is true then figure out that your value proposition solves that big problem or not. For this you can sit with a target customer and figure that out. If your value proposition is not good enough then figure out what could be a good value proposition.
3. If you are convinced that it is a good value proposition then it is just a question of how you deliver it to the customer. And the most important thing is that you have to be convinced whether it is a good value proposition or not - and if you are then hang in there for as long as it takes and figure out a delivery method.
Having said that, I think the only time you need to call it quits is when you want to - and if you not want then there should be a way to make it fly, you just need to figure out how.
1. Is it a big hill after all - your customers might want something else. If it is not a big hill then figure out what a big hill is and reorient-realign-refactor.
2. If 1.is true then figure out that your value proposition solves that big problem or not. For this you can sit with a target customer and figure that out. If your value proposition is not good enough then figure out what could be a good value proposition.
3. If you are convinced that it is a good value proposition then it is just a question of how you deliver it to the customer. And the most important thing is that you have to be convinced whether it is a good value proposition or not - and if you are then hang in there for as long as it takes and figure out a delivery method.
Having said that, I think the only time you need to call it quits is when you want to - and if you not want then there should be a way to make it fly, you just need to figure out how.
..just my two cents