Perhaps you feel that your idea doesn't help someone else, even if it is interesting to yourself (hence it's easy to do work for others). Convince yourself either the idea/product would help people (ask if people are interested?) or do it for fun/hell of it. Otherwise, cut your losses.
How to beat procrastination: http://news.ycombinator.com/item?id=2185174
Perhaps you feel that your idea doesn't help someone else, even if it is interesting to yourself (hence it's easy to do work for others). Convince yourself either the idea/product would help people (ask if people are interested?) or do it for fun/hell of it. Otherwise, cut your losses.