What does it mean to “long” for someone? It means that a person is unsatisfied or unfulfilled because there is someone he or she very much wants to be near, to hear that certain voice, to experience that special presence.
Usually, particularly when the object is someone very much loved by the person who is longing for another, there is hardly a waking moment when that person is not on the mind of the one who is “longing for.”
Have you ever been under water for a period of time that is longer than you had expected? You know, as the time ticks away, how desperate you become to reach the surface and breathe the air. The greater the time you are under water, the more you long for a breath of air until that desire overwhelms you, and you rush to get to the surface as rapidly as possible. You have no other thoughts but quenching your need for air.
That is what it means to “long for God.” In another context, it is what it means to “hunger and thirst” after righteousness with the same desires that lead us to quench our physical need for food and water.
How many of us are content to give God only a brief moment of our time, a hasty prayer before a meal, a few coins in the offering plate on Sunday, and forget about Him the rest of the time?
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.