Bhagavad Gita

ಯಾ ನಿಶಾ ಸರ್ವಭೂತಾನಾಂ ತಸ್ಯಾಂ ಜಾಗರ್ತಿ ಸಂಯಮೀ।
ಯಸ್ಯಾಂ ಜಾಗ್ರತಿ ಭೂತಾನಿ ಸಾ ನಿಶಾ ಪಶ್ಯತೋ ಮುನೇಃ ॥೬೯॥
yā niśā sarvabhūtānāṃ tasyāṃ jāgarti saṃyamī|
yasyāṃ jāgrati bhūtāni sā niśā paśyato muneḥ ||69||

Gist of the sloka:
That which the regular person thinks as night, the one who has achieved control over senses would see it as day. Where others are seeing light, the seeker would see night.
That which for a regular person is day, the truth seeker would find it as night. That which the world feels as night, the seeker would find it as day. The regular worldly affairs would be night for the seeker. He would have little interactions or attractions with the world. He would appear like a innocent child. He might even appear like a idiot or crazy person to normal people – world might have no clue to his inner beauty. For the seeker, he would have found all the happiness internally and would be savoring it.
Once the seeker has found the Lord inside him, everything else is darkness for him. Looking at the beauty of the Lord, he would be mystified and forever involved with it. To seek the Lord, one should be engaged in hearing of Him through the sacred books. After hearing one should keep thinking about the knowledge learnings. One who keeps thinking constantly about the Lord is called “Muni”. For he is the one who has seen the lord or would see him.
In today’s world, to identify such persons is very difficult. Not all the sidda purushas [one who has acquired siddas powers] are real seekers. They are just miracle makers generally. For the real seeker never demonstrate their powers unless it’s extremely necessary to reinforce Lord messages. Those who have constantly strived to understand the truth [Muni] will become stitha-pragna.