a millstone around one's neck

The phrase "a millstone around one's neck" refers to a burdensome or oppressive situation or responsibility that weighs heavily on someone. It originates from the literal meaning of a millstone, which is a large, heavy stone used in a mill to grind grain. In this metaphorical context, it implies a tremendous burden that hinders or restricts someone's progress, similar to how a large stone would hinder movement if tied around someone's neck.