It's hurtful to cheat on your spouse.
John, who is married, is talking to Wendy at a bar when Wendy suddenly tells him she's attracted to him and asks him to sleep with her.
John wants to respond to Wendy's question.
John declines Wendy's request and reminds her that he is married and faithful.
John agrees to sleep with Wendy, and they leave the bar together.
John's wife is told that John declined a woman's advances and feels happy and safe in their relationship.
John's wife finds out about the affair and is deeply hurt and ashamed and ends their relationship.