It's immoral to betray your partner's trust.
Jack's friends invite him to go on a guys' night out and his girlfriend admonishes him not to do something that would damage their relationship.
Jack wants to go out with his friends.
Jack goes out with his friends but doesn't pursue any women while they're out.
Jack goes to a bar with his friends and ends up making out with a girl he met there.
Jack's girlfriend is happy that she can trust Jack to be true to her.
Jack's girlfriend is devastated when she learns that he kissed another girl.