It's wrong not to be happy for your friends.
John is meeting up with a friend who told john that they had some exciting news.
John wants to hear the news.
John finds out that his friend is getting married and acts excited and congratulates his friend despite feeling a tad jealous inside.
John finds out that his friend is getting married but doesn't show any outward emotions because he is jealous of his friend.
John's friend is happy to have shared the news and continues on his emotional high.
John's friend is disappointed in John's reaction and his mood is soured.