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.
Several years ago I focused on a certain Benjamin Butler in an 1850 census enumeration as being “mine.” Using that enumeration as the starting point, I searched other records and made progress. I located a fair amount of information. One problem–I didn’t track WHY I thought this 1850 census entry was for the correct person. What I found later all tied to the 1850 guy, but not to the one who was really “mine.” It took me hours to reconstruct my reason and that was time wasted.
Fifteen minutes to write up my reason to begin with would have saved me time later.