Jiu jitsu is a sport with near-infinite breadth and depth. There's a reason it takes 10 years or more for most people to earn a black belt... there's just a hell of a lot of knowledge to learn and apply. Anything we can do to make this learning process easier or more efficient needs to be embraced, and Soviet Psychologist Lev Vygotsky's (1896-1934) "zones of proximal development" is one such idea.
The idea is pretty simple and is represented by this diagram:
The middle white triangle represents what you've already learned through previous training. The black area represents all the knowledge that exists about jiu jitsu (note this is not drawn to scale.) The red area represents the knowledge you CAN learn based on your present abilities, usually with outside help. In our sport, that usually means our coaches, but that help can also come from teammates, instructionals, books, etc. Once we do master the area in red, we'd change it to white and expand the red triangle out a little bit farther.
Theoretically, this concept is simple and, without any conscious effort on our part, is already being used by all of us whenever we learn something new in class (or anywhere else.) Practically, though, this concept can get a whole lot more effective if we consciously define exactly what that red triangle entails. The red triangle usually consists of the stuff we know we don't know, while the black consists mostly of that which we do not know we know. Since we cannot know what we don't know, we need to focus on what we know we don;t know. You know?
So how do you decide what's in the white triangle?
Step One: Start by assessing the two biggest your biggest holes in your game and write them down. Does your guard retention suck? Do you have trouble finishing an Americana? And let's face it- we could all work on our takedowns. If you have trouble with this step, just ask the training partners you roll with regularly. Now write down one strength of your game. Write that down, too.
Step Two: Talk to your coaches. Tell them explicitly what you would like to work on, ask them for advice, and ask if they could pay attention to those things. Your coaches are in the best position to give you expert feedback and instruction, which is the secret boost to utilizing Vgotsky's Zones of Proximal Development.
Step Three: Put in the work. Now you train. While training, focus on these three things whenever possible. When you feel you've made adequate progress in correcting one of the two weaknesses or you've improved your strength to the point where you can use it on almost all of your training partners, go back to step one and identify something new. Lather, rinse, repeat.
Give it a shot. If this process works well for you, tell us the story in the comments!