Silence

 https://www.orthodoxbend.org/silence-is-the-school-of-the-soul/

...He went on to say, “For it is no more possible to write in wax without first smoothing away the letters previously written thereon, than it is to supply the soul with divine teachings without first removing its preconceptions derived from habit.” For to reach that end, “solitude gives us the greatest help, since it calms our passions and gives reason leisure to sever them completely from the soul.”...