According to Hindu mythology, observance of mahashivratri vrat with discipline helps a devotee to control the two great natural forces that afflict man, rajas guna (the quality of passionate activity) and tamas guna (the quality of ignorance). When a devotee spends an entire day at the feet of the Lord and worships with sincerity, his mind is controlled and evils like lust, anger and greed (born of rajas) are subdued. When a devotee observes a waking vigil throughout the night (jaagran) he conquers the evils of tamas guna as well. It has also been mentioned in the scriptures that when a devotee observes a round of worship every three hours, the Shivaratri Vrata becomes perfect.
Devotees of Lord Shiva consider Shivaratri fast to be extremely auspicious, greater than performing an ashwamedha yagna. Devotees who observe a fast on Shivaratri with sincerity and utter the name of Lord Shiva (om namah shivaya) with perfect devotion are absolved from all sins. Such devotees reach the abode of Lord Shiva and live there happily for all time. Such a devotee is liberated from the cycle of birth and death.