Chapter thirty-three of the Tanya prescribes an exercise for generating joy—and it is available to every person, regardless of spiritual level.
Concentrate your mind and consider: God permeates all worlds, upper and lower. This physical world, right here, is filled with His glory. Everything you see—every object, every person, every particle of matter—has no independent reality. In God's presence, all things are nullified the way sunlight is nullified within the sun itself. The light exists within the sun, but you cannot see it because it is absorbed by its source.
That, says Rabbi Schneur Zalman, is the relationship between the universe and God. The universe exists within God the way light exists within the sun—real, but invisible against the infinite radiance of its source. Before creation, God alone filled the space where the universe now exists. After creation, nothing changed from God's perspective. He is still alone, still singular, still infinite. The universe adds nothing to Him.
When a person truly contemplates this—not intellectually but with the full weight of conviction—joy arises spontaneously. Why? Because this contemplation is the experience of closeness to God. And closeness to the Infinite King is the greatest possible joy.
The Tanya offers a parable. A common person—lowly, insignificant, dressed in rags—is brought before a king. The king accepts his hospitality, enters his home, stays with him. The joy of that commoner would be beyond description. How much more so, the Tanya says, should a person rejoice when the King of all Kings, the Ein Sof (אין סוף), whose glory fills the entire universe, chooses to dwell in the soul of every person who studies Torah and performs mitzvot (commandments).
This joy is not emotional ecstasy. It is the steady, deep gladness of someone who knows where they stand—in the presence of the Infinite, invited to host God in the small city of their body. That knowledge, fully absorbed, is enough to generate joy even in the darkest circumstances.