it’s (only/just) human nature
From Longman Dictionary of Contemporary Englishit’s (only/just) human natureit’s (only/just) human naturespokenNATURAL used to say that a particular feeling or way of behaving is normal and natural → human natureExamples from the Corpusit’s (only/just) human nature• It's human nature to put off doing things you don't like to do.• But it's human nature that people-male or female-will do what they are allowed to get away with.