Keeping track of your progress is paramount if you plan to improve in your jiu jitsu game. Most high level Black Belts and World Champions know that if you improve your technique by only 1% each day then the compounding effect will make you proficient in the gentle art at a very high level.
Keeping a series of techniques in your head is a complex matter. This is human chess after all, for every attack there is a defense for every sweep, takedown, pass, submission there is a counter...and counter to that counter. It makes much more sense to keep taking notes than trying to remember what you did, even if you just did it. How many times do you get to the next class after practicing a sweep and you can't remember the vaguest detail!
Also, when you review, as you should periodically, some techniques you will identify as being easy to perform and fit your body-type better. These techniques I put a checkmark in the corner of my journal and come back to drill some more.
The techniques that present a challenge should have an X in the corner of the page, meaning you need to revisit this in more detail maybe with your professor or coach. This art form is a process yet it is system driven. One thing leads logically to another. It’s position-transition-submission.
The logic, though, is lightning in a bottle. It needs to be grasped and placed into the correct place in the puzzle or the puzzle will not unlock.
Remember how a technique was working really well and you were catching everyone or passing guards, then a couple of weeks later it stopped working?? What happened? Probably, a detail you were applying has now been forgotten. Wouldn’t it be great if you could go back and retrieve that detail, well, now you can with the Zen Jiu Jitsu Training Log.