It's unacceptable for people to cheat on their romantic partners.
Stacey is not happy in her relationship because of the constant problems she faces with her partner.
Stacey wants to have a more fulfilled romantic life.
Stacey breaks up with her partner and cites the change in their relationship.
Stacey gets involved with someone else while she's still with her partner.
Stacey's partner is able to move on given the reality of the situation.
Stacey's partner finds out about the infidelity and it weighs on him for a long time.