Jiu-jitsu puts you completely in the moment, where you must have a complete focus on finding a solution to the problem. This trains the mind to build that focus, to increase your awareness, your capacity to solve problems.
Manhood begins when we have in any way made truce with Necessity; begins even when we have surrendered to Necessity, as the most part only do; but begins joyfully and hopefully only when we have reconciled ourselves to Necessity; and thus, in reality, triumphed over it, and felt that in Necessity we are free.