In this video, Phakchok Rinpoche discusses the four levels of transformation. The first level of transformation is the purification of karma, the bad habits that we have accumulated throughout our lives. Buddha Shakyamuni taught the Ten Nonvirtues to make it clear what obscurations we must transform. These ten nonvirtues are subsumed into the three categories associated with actions of body, speech, and mind.
To be able to transform our obscurations, we need to take responsibility for our actions and believe in the inevitable results of our karma. Phakchok Rinpoche explains here that not believing in karma means that we are not taking responsibility for the effects of our actions.
You can read more about the role of Buddhist ethics in transforming the mind in this teaching from Khenpo Gyaltsen.