When was the last time you reviewed material or information you obtained in the early days of your research? Did you neglect to indicate where something was originally located? Did you simply copy something from a website or book without considering that it could be wrong?
Most of us did those things early in our research--but are there still items of that type lurking in your files or database causing those "brick walls" we all complain about?
Now that you're a little more seasoned, review what you did in the early days and see if you still agree with yourself.