Hi Tipton:
Keeping a record is useful to reflect, to comment to oneself, to record thoughts and desires, or maybe, a bit more functional, such as records of good ideas for lessons, notes from past classes that were very successful, or observations about different classes over time.
It's not a requirement to journalize, for some it's just not their style. But for others, it's a very underused tool successful teachers use for self awareness and improvement.
Regards, Barry