God wants us to long for Him because it is in that longing that we are fulfilled and overwhelmed by God and the reflection of His Son, The Lord Jesus Christ, in our lives. We are never more fulfilled than when our longing for God is met by His Presence in our lives.
https://bible.com/reading-plans/16184/day/3?segment=0
Psalm 63, prayed when David was in the wilderness of Judah, expresses the intimate relationship between God and the worshiper. Separated from God, the psalmist longs for the divine life given in the Temple, which is based on a close relationship with God.