The person covering two roles still has one ordinary day’s attention.

Responsibilities can be added on paper without anything being added to the person. Two jobs, or a job and the care of a relative, still have to fit inside the same waking hours and the same finite attention, so what actually happens is that something quietly gets less. Usually it is the part nobody is measuring, which for a while is rest.

If you are carrying two things, say plainly which one will be slower rather than letting both fray. And if you are the person handing work out, ask what will be dropped instead of asking whether it can be absorbed.