Bhagavad Gita, Chapter 2, Verse 60

The turbulent senses, O son of Kunti, can forcibly carry away the mind even of a wise man striving for perfection.

Even someone genuinely trying to stay disciplined can still get swept off course. The senses are that strong.

This isn't a warning aimed at the careless, it's aimed at people who are actually trying. Good judgment and real effort still aren't automatic protection against getting pulled off track.