Anna Lembke

Oxytocin, a hormone much involved with falling in love, mother-child bonding, and lifetime pair bonding of sexual mates, binds to receptors on the dopamine-secreting neurons in the brain’s reward pathway and enhances the firing of the reward-circuit tract. In other words, oxytocin leads to an increase in brain dopamine, a recent finding by Stanford neuroscientists Lin Hung, Rob Malenka, and their colleagues.
After his honest disclosure to his wife, followed by her expression of warmth and empathy, Jacob probably experienced a spike in oxytocin and dopamine in his reward pathway, encouraging him to do it again.

any high-dopamine substance or behavior we ingest too much of for too long

The o in DOPAMINE stands for objectives for using. Even seemingly irrational behavior is rooted in some personal logic. People use high-dopamine substances and behaviors for all kinds of reasons: to have fun, to fit in, to relieve boredom, to manage fear, anger, anxiety, insomnia, depression, inattention, pain, social phobia . . . the list goes on.