It is important somewhere to keep track of your research logic as you progress. Otherwise you might not remember “why” you are researching a certain person.
While on a recent research trip, I focused on a certain Benjamin Butler in the 1850 census as being “mine.” Using that enumeration as the starting point, I searched other records and made research progress. A stack of papers, a file full of digital images, and records located were the end result. One problem–I didn’t track WHY I thought this 1850 census entry was for the correct person. It took me hours to reconstruct my reason. That was time wasted.
When I decided the 1850 guy was “mine,” I should have written down my reasons. They were valid reasons. Resurrecting them took time–time that could have been spent in a better way.