Normal human beings used their brain 1 to 2%, indulgence in spirituality as detailed in Bhagavad Gita results in full activation of brain 100%. One immediately becomes an enlightened one, a bodhi, a Jina… a Mahavira forever.
Spirituality was all about removing the clutter within our thought process, reaching state of Nirvikalpa Samadhi (when not a single thought entered our brain uninvoked).
For achieving this state human beings need demolishing their ego in totality. Only then we can realize, feel presence of spirit, consciousness within our heart.
Spirituality further demands our establishing total control over five senses and mind.
Practicing absolute celibacy for a minimum period of 12 years in continuation is another necessity. Practice of absolute celibacy results in full awakening of kundalini shakti, the coiled Serpentine energy lying dormant in base of spine!
The awakening of kundalini results in activation of dormant lying portions of our brain in stages. One starts scaling higher levels of consciousness, experiencing states of inner calm, total bliss.
And finally one reaches a stage when kundalini climbs to Ajna chakra. That very moment Sahasra Pushpa (thousand petalled Lotus) existing in our brain behind forehead opens fully. One immediately gains enlightenment.
All enlightened ones like Mahavira, Gautama Buddha, Jesus Christ and Prophet Mohammed after reaching state of enlightenment used their brain 100%.
The moment human brain activates 100% it connects to the universal mind. One finally becomes knower of all. Sacred texts like Bhagavad Gita and Upanishads become like ABCD.