The spiritual focus of the circle is the flame of the lamp, which is always lit during rituals, and which resides in the middle of the altar top. The absolute magical center of the circle is the invisible point where the flame of the lamp tapers up and vanishes into infinity. Usually a ceramic or metal oil lamp is used, but a candle is acceptable. Some groups maintain a perpetual flame on their altars. This is beyond the reach of small circles or individuals, but the flame should be maintained without failing in the astral temple in the mind of each ritualist. This is the true occult perpetual lamp.
The flame is the focus of the awareness of those working the ritual. They direct their prayers to it and meditate upon it. The point at which it disappears into infinity marks the doorway in the Veil of Unknowing, which the ritual is designed to open. The flame should be conceived by the Magus as burning in the center of his or her being, throwing its light across the circle of self. When the circle is filled with light, the self is purified and exalted.
Llewellyn’s Complete Book of the Rider Waite Smith Tarot by Sasha Graham
You can hear or read something many times and not "get it." Until that one time when you do. Maybe it was the way it was said. Maybe your brain was poised to receive....