It's impolite to curse at a friend.
Harry loses to his friend in a competitive one versus one video game.
Harry wants to make a comment to his friend.
Harry praises his friend for winning and tries harder to win next time.
Harry curses at his friend and complains about losing to him.
Harry's friend loses to Harry next time but still enjoys his time with Harry.
Harry's friend does not appreciate Harry's behavior and simply leaves.