A devout Jew clears his mind of harmful thoughts and worldly ideas.  He visualizes inspiring historic scenes like the Jewish people gathered at Mount Sinai, Avraham and Yitzchok on Mount Moriah, the Tabernacle, the service of the Beis Hamikdash, the glory of the Shechinah resting in the Beis Hamikdash, and the like.  He memorizes these mental pictures, so he won’t forget them.  He banishes any thoughts that may confuse him and raise doubts, and reins in anger and lusts, so that these emotions don’t lead him astray.  ~ Kuzari