People usually "fall in love" with ideas, which is why its so hard to pull away from it. Its hard to be rational and objective when you're in love. This isn't so much of an issue in a relationship (in love with a person) because how you feel is what matters. However, in a startup, what matters is how the customers feel, and that love potion will be your Archilles heel if not treated carefully. I generally try to fall in love with problems before an idea (solution). When the idea comes before the problem, its been disastrous. Customer Development helps, but its still a rough ride.