The Srimad Bhagavatam explains that Krishna as caitya-guru helps to surrender to Him. Caitya-guru means the Lord in the heart. However, before we are able to perceive the Lord's dictations, we must purify our existence. To purify our existence, we must accept some discipline by which our hearts can become cleansed. The example is of Lord Brahma practising meditation upon hearing the syllables "ta-pa". The result of Brahma's obedient austerity was that the Lord personally revealed Himself to him and showed him the expanse of the Vaikuntha planets. Because Brahma accepted his guru's discipline, everything was revealed to Him:tene brahma hrda ya adi-kavaye. The point to note is that although Lord Brahma agreed to become disciplined, he did not perform whimsical austerities. The auterities he chose to practise were based upon a superior dictation. The spiritual master is the external manifestation of Supersoul, and he instructs us consistently with the dictations of caitya-guru. By accepting guru's discipline and purifying our existence, we can learn to contact the Lord in the heart. We conquer the mind not by whimsical activity but by engaging in the Lord's service under our guru's direction.
LFD Vol 1, How does the disciple become disciplined?, Pg 63, several paragraphs.