How Can You Affix Hashem in Your Mind?

A person can put the Oneness of Hashem into his mind through practice, thinking a good deal about how the whole world cooperates to do the will of Hashem... This is a visualization of the thought that Hashem is One. If a person follows that approach, visualizing a concept and thinking about it frequently, it ultimately becomes part of his permanent mindset. — Ohr Avigdor Hakdama