The yogic sutra tajjapah tadarthabhavanam explains that Aum should always be repeated with extreme respect and devotion and it needs to be chanted unremittingly. With incessant practice and reverence, a sadhaka can attain realisation of the Divine Being.

tat that (aunt)
japah muttering in an undertone, whispering, repeating
tadarthabhavanam its aim, its purpose, its meaning with feeling, its identification

The mantra aum is to be repeated constantly, with feeling, realising its full significance.

Constant, venerating repetition of the pranava aum, with reflection on its meaning and the feeling it arouses, helps the seer to reach the highest state in yoga.

Words, meaning and feeling are interwoven. As words are eternal, so are meaning and feeling. Meaning and feeling vary according to one`s intellectual calibre and understanding. This sutra expresses the devotional aspects of the seed mantra aum.

Japa is repetition of the mantra, with veneration and realisation of its meaning. Practice of japa unites the perceiver, the instruments of perception, and the perceived - God. The mantra aim is considered the Sabda Brahman (Word of God, or Universal Sound) to be known with the organs of perception and action, mind, intelligence and consciousness.