About those past misdeeds that we have performed but cannot recall, we can contemplate on them like this: “The misdeeds that I have committed since beginningless time, whether intentionally or unintentionally all of them are wrong. As if they were poison I have taken, I feel the greatest fear and regret for my actions, and vow never to commit them ever again.” In this way, all our negative karma can be changed into mutable karma. The significance of such resolve cannot be overstated. Otherwise, if we fail to do this, any karmic effect is possible.
~ Luminous Wisdom Book Series 1: On Cause and Effect