The owner of the company was a bit concerned that I was taking a lot of time to develop a time estimate for a purchase order system that I am building. Below is my response.
One thing that I didn't make clear in the meeting is that I use estimates as a personal time management tool. Once someone understands how to put together a time estimate, it's actually a ridiculously easy thing to do. With more practice, the times become more accurate. I've found that when I put together a good estimate, I have most of my basic system design in place (one can't estimate without knowing what one's implementing) and the work is much easier to do.
When I work on a given task and I see that I've allotted seven hours for it, I find it easier to keep on task and not get distracted because I have a deadline that is self-imposed. Because my time estimate is my promise to meet a certain goal, I feel very invested in keeping my promise.