The phrase divide and conquer is a common English idiom. Just like you said, it means to break a problem or task down into small pieces and then solve them one by one so that they feel more manageable than one big task.

Alternatively, it can mean to divide work between members of a team so that no one has to do an overwhelming amount.

Etymology: "Divide and Conquer" comes from a history of armies and imperialism. If you (a military general) are facing a larger and stronger army, you might win by splitting the other army up and beating it in small pieces instead of all at once.