Solitude is not empty when your mind has somewhere meaningful to go.

Alone time only feels empty when there is nothing in your mind worth going toward. Someone with a real question, a project, or something they are working through is not idle in solitude; they are occupied by something internal, and the hours have plenty in them.

So it helps to have something running: a question you are living with, a thing you are making, a subject you are learning. Not to be productive, but so that quiet has somewhere to go. Choose one and let it be what your mind reaches for when there is nothing else.