What did John Stuart Mill fear?

religious freedom

lifestyle choices

tyranny of the masses

pursuit of happiness

He lost the pursuit to happiness. He felt that striving towards his goal in life would not make him happy, he felt depressed and almost committed suicide. But he regained his sense of purpose and happiness after being motivated by William Wordsworth's writings about compassion to people would stimulate the happiness that he wanted so he made a decision to continue his dreams for the society.