I am a big believer in keeping a training log, as well as a training journal. I think it is critical to our efforts to become more capable to keep good track of every stumble, every success, and every thought or discovery. There are tons of logbooks and journals out there, but I use these. They are not cheap but they are incredibly well organized to help you keep logical track. I think there is an end of the year sale now going on too.
(FYI, I get zero money or gifts from this place. They only know of me as a customer)