The failure of early narcissism leads to shame. Shame is an unmet childhood need and when a child grows up and becomes an adult, the need grows until it is fulfilled by someone or by some behavior.
When a narcissistic adult feels a negative emotion, they will act out with alcohol, drugs, sex, gambling, shopping, etc. over the unmet needs related to shame. Even when they have a positive emotion, they may act out, feeling they don’t deserve to have goodness and positivity in their lives.
Addiction is a futile attempt to get a person’s needs met. In fantasy a person can control the situation and never have to feel they’ve failed. People have affairs and act out sexually because it’s a controllable situation, “I get my needs met and don’t have to deal with the demanding chaos at home.”