Romanticism is a reaction against the intellectual climate that preceded it. Reason rules in the neoclassical period and in the Age of Reason, and during The Enlightenment. These are times of satire, of concentrating on the big social and political and religious issues.
Romanticism concentrates on the personal, the individual, intuition, the imagination. Romanticism stresses the opposite of what came before in almost every thought it expresses. Jonathon Swift takes on the entire British government, wealthy English, and wealthy Irish, to combat poverty, while Blake writes about the mistreatment of chimney sweeps. Romanticism breaks the issues down to the personal level.
One more example: Deism is prevalent in the Age of Reason, etc. Man is seen as preeminent and any creator is indifferent. Man's future is in the hands of man. Romanticism stresses an intuitive or transcendent connection with nature. Man communes with nature and is changed by it. Romanticism is interested in that which is beyond human understanding and reason.