Tanya Chapter 33 part 3

When we attain awareness of the Divine unity, aside from the joy that we feel in the intimate closeness to Hashem, we become an abode for Him. And that is actually our purpose! This faith in G-d's unity is so transformational that it breathes new reviving life into us, taking us high above all obstacles. The joy is doubled and redoubled when we consider that our awareness of the Divine intimate presence brings joy to the Creator Himself! So we rejoice together with Him, as He rejoices in the abode we’ve created for Him down below.