I have hit this wall as well. Half way through a project I stop and ask myself:

Who is going to use this? Does anyone have a need for this? How do I get people to use this instead of X? Can I monetize this?

Half way through working a project I sometimes give up because I'm not sure I would even use it. That's the problem I'm trying to solve, figuring out what I can build that compels me to see it through and solve a real problem even if it's not MY problem.