I keep one mostly for personal enjoyment, but it can have some learning benefits such as at what water levels did you catch fish. I kept one fairly well from 1980 to 1988 or so until the birth of my third child, and my wife demanded more child time on my part and the journal went. I started keeping it again about a year and a half ago. I really have fun reading through those earlier entries, some great memories, many of which I had forgotten about.