Sankaracarya's Vivekachudamani 449

अहं ब्रह्मेति विज्ञानात्कल्पकोटिशतार्जितम् ।

सञ्चितं विलयं याति प्रबोधात्स्वप्नकर्मवत् ॥

ahaṃ brahmeti vijñānātkalpakoṭiśatārjitam |

sañcitaṃ vilayaṃ yāti prabodhātsvapnakarmavat ||

(Sankaracarya's Vivekachudamani 449)

"I am Brahman"--with this Realization, the actions of hundreds of millions of world cycles come to naught, like the actions of the dream-life on waking up.

Brahma-siddhi means that one should know that he does not matter; he is a pure soul. There are different kinds of yogīs, but every yogī is supposed to engage in self-realization or Brahman realization. It is clearly stated here that unless one is fully engaged in the devotional service of the Supreme Personality of Godhead one cannot have an easy approach to the path of Brahma-siddhi. Unless one come to the platform to surrender to the Supreme Lord without any condition, then one's past present, and future birth will become null and void.