Jon Wise - Embracing My Inner Geek: Part 2 - The Job:

"So after months of wearing jeans, chugging caffeine, cluttering your desk with sketches and reference material, you clean yourself up, put on a nice pair of pants, comb your hair, and sell again. Although most organizations have a sales force and a marketing department, a savvy customer will invariably want technical details that a non-coder can’t supply. As a lead developer on a project, it falls to you to instill confidence, to speak articulately and passionately about the appropriateness and worth of your solution.
Again, as before, pride is a weakness here, because no matter how good you are, someone will always ask if your software can do something it can’t — user’s are never really satisfied. So you think back to the design process, you remind them when they had a part in the decisions, and you attempt to impress upon them respect for the solution you have now, while acknowledging that there will always be a version 2.0."