On the other hand, know tamas, which deludes all embodied beings, to be born of ignorance. O scion of the Bharata dynasty, it binds through inadvertence, laziness and sleep. (Bhagavad Gita, 14.8)
I [Sanat Sujata] say, inadvertence is death itself, and mindfulness is immortality. It is due to inadvertence that the asuras were subjugated [by defeat and death], and it is by virtue of vigilance that [the gods] are immortal. It is not death that devours like a tiger, for the nature of death is unfathomable. (Sanatsujatiya, 4-5)
If the mind ever so slightly strays from the ideal and becomes outgoing, then it goes down and down, just as a ball inadvertently dropped on the staircase bounces down from one step to another. (Vivekachudamani, 325)
A man must be extremely careful during the early stages of spiritual discipline. ‘You see, a man must not sway his body while climbing to the roof; he may fall.’ (The Gospel of Sri Ramakrishna, 604)
Always be careful. A careful person is not subject to grief. Never forget that. Prarabdha karma cannot torment a person who is always alert. (Spiritual Treasures: Letters of Swami Turiyananda, 31)