Guest post by Belgian BJJ black belt Wim Deputter, head instructor at Brasa Team Belgium.  https://www.instagram.com/wimdeputterbjj/

What is the single most important thing you should learn in Jiu Jitsu?

It isn’t a technique or a bunch of techniques. It is one simple concept. Without this one concept, your techniques wouldn’t be as effective. Everything would take a lot more explosiveness, strength and speed.

In my opinion, the single most important thing to learn and focus on in Jiu Jitsu is the Art of Connecting your own body to that of your opponent.
By using grips (hands), hooks (feet) and form-tension you can latch on to your opponent, creating one unit with his or her body.

Once we are properly connected, the opponent loses the ability to move independent of your body; you effectively slowed down the fight and took away the ability of your opponent to use his physical attributes to their maximum advantage.
When the opponent moves, he has to move the unit as a whole.
An opponent trying to muscle out or break free will at the very least spend a lot of energy.
More experienced grapplers, will be able to see and use the movement of the opponent as opportunities for favorable transitions.

At a basic level Jiu Jitsu is nothing more than establishing an initial connection, waiting till the opponent moves, transitioning to a better body position while maintaining connection, right until we arrive to a position where we can submit.
At an advanced level our opponents are more patient and aware; your opponent will not always move first. Now we have to use angles, levers and pressure to make our opponent uncomfortable enough so he moves. Movements we can again use for favorable transitions.
At an elite level, you can grapple with less connection. The more disconnected, the more you will need to use your physical attributes and the more risk for injury.
Ultimately to submit we will always need connection.

As you get older, physical attributes diminish. Connection and patience become the only ways of high percentage defense and offense.

With beginners I always focus on connection first. Connection is the grammar of Jiu Jitsu. Positions are just different ways of expressing connection. Techniques are ways of transitioning. Techniques are the vocabulary of Jiu Jitsu.