[hopeless]

Seth Godin has a book ("The Dip") about knowing when to quit and I should have read it much earlier, during my PhD.

Essentially, the absolute worst outcome is to stick with it and give up towards the end (which is what I did). Then you've got all the downsides of wasted time/investment and no upside. Quitting early isn't the worst possible outcome because at least you've saved yourself money & time.

My takeaway was that the earlier you commit to quitting or sticking, the better. Either commit to quitting now or decide to stick with it for the very long haul; even if that means going back into full-time employment, raising investment money, hiring staff, incrementally switching focus until the thing sells.