初生之犊不畏虎/ 初生之犢不畏虎chūshēngzhīdúbùwèihǔ(also chūshēngzhīdúbúwèihǔ)the fearlessness of youth
Literally "a newborn calf does not fear the tiger"; describes a young person who is bold and courageous because they lack experience or are not yet aware of life's dangers.