A shelf will hold almost anything you give it, which is exactly the problem. Emptiness feels like an oversight, so objects accumulate until every level is full and none of them can be seen properly anymore.
The dish that sits alone on a plain shelf asks to be noticed in a way it never could beside a dozen other things. Its glaze, its slight unevenness, and the way morning light catches one edge all become visible again once the shelf stops competing for attention.
Restraint here is not about owning less. It is about choosing which objects deserve height and light and space around them, and returning the rest to a drawer where they can wait for their own moment.
A shelf that holds three considered things will usually say more about a room than one that holds twenty. Leave gaps. Let the wood show. A shelf, like a sentence, often improves with fewer words.