You can contemplate the eighteen realms at any time. You are not limited to meditating on a cushion. When you see something, directly perceive it as empty; when you hear something, directly perceive it as empty; when you eat something, directly perceive it as empty; when you walk, talk, sleep or think, directly perceive these acts as empty. This is direct contemplation. If you can do this, true wisdom will arise, and whatever karmic retribution remains will also be empty, because there is no more attachment.

If, like most of us, you have not gotten to that point, then you still have attachment. Karmic retribution still applies, and you experience suffering instead of wisdom. It is because of suffering that we must use the methods of contemplation described in the Heart Sutra. We must contemplate that the eighteen realms are empty. Slowly, emotional afflictions will lessen. If we are completely successful, emotional afflictions will disappear.