How do you know when you're going 100% on the wrong thing? * I have a friend who has committed the last five years or more to his system. It's good but not gr

How do you know when you're going 100% on the wrong thing? * I have a friend who has committed the last five years or more to his system. It's good but not great, in my opinion, and while he has made some traction, paid users, etc. I feel like he's going nowhere with it. I don't tell him, of course. * I have another friend who spent more than a decade on some technology. It seems to me earth-shaking stuff, but it's become a bete noire to almost everyone who knows him because they think he should have given up already.