Confessing daily mistakes especially before going to sleep is the way to keep samaya pure
We break samaya very easily therefore we are making mistakes every day. Therefore, we need to confess every day at the beginning of the day, at the end of the day and in the middle of the day. With mindfulness you are able to aware whenever you make mistakes and so you confess whenever you aware of anything. But most of the time we are not aware of [our] mistakes. So at least before you go to sleep you have to think of what you did [during the day]. If you remember any mistake you made, confess. If you don’t remember it is still there. You don’t remember doesn’t mean you did not do any wrong things. Therefore, before going to sleep, you must do some things like [reciting] Om Benza Satto Hung, or Hundred-Syllable. Such confessions are very important. That’s the way to keep one’s samaya in pure way.
Hungkar Dorje Rinpoche, “Devotion To Guru Rinpoche – Key To Siddhis”