Mind training is based on the idea that two opposite mental factors cannot happen at the same time. You could go from love to hate. But you cannot, at the same time — toward the same object, the same person — want to harm and want to do good.

Ricard is describing a core premise in Buddhist-derived contemplative training: mental states have incompatible valences, so cultivating one can inhibit its opposite. The quote contrasts the rapid mutability of emotion (love can flip to hate) with the claim that, in a single moment and toward the same target, intentions of benevolence and malice cannot fully co-occur. This frames meditation and ethical practice as a kind of “mental hygiene”: repeatedly strengthening prosocial attitudes—kindness, compassion, goodwill—reduces the likelihood and intensity of harmful impulses. The implication is practical and moral: inner training is not merely self-soothing but a method for reshaping intention, and thus behavior, by replacing destructive motivations with constructive ones.