Money can't buy it, fame can't dampen it, physical pleasures can't satisfy it. The longing is for a purpose to their lives. A reason to exist. You can go on living for years without one, and your life might even seem pretty good. This presents two questions that you should ask.
Few people have a huge wedding without making plans.
In the same way, your eternity is something you should consider. You might believe in Reincarnation, but think about it. You'll be reincarnated anyway. You see, God's not warm and fuzzy. Warm and fuzzy Gods don't let their son have big chunks of his flesh torn off by a Roman flail and then let him die an agonizing death on a cross as the crowds jeered.