Japa for a condusive mind. repetation of the mantra which can be your "ishta devata" any name of the "Iswara" gives a predictability of ones next thought. if one becomes aware of it one can see the thoughts are objectifiable like our own body.see your thoughts and by doing japa one can extent that alertness to all other thoughts.This way the mind will abide in oneself.It is called a peaceful mind which is essential for further growing in clarity to get the "Atmajnanam" self knowledge. Bhagavad Gita talks about it. There Sri Krishna gives the knowledge of the self also the methods to prepare oneself ready for it. Raga dvesha management through yoga buddhi is elaborately taught. we will see that in study of Bhagavad Gita. Japa happens to be an important aspect to accomplish the readiness of the mind for self knowledge.