They run and chase and then run some more. Some people have commented on how great it would be to bottle some of that energy and save it for later in life. As we grow older, our batteries drain faster. Even simple tasks like going upstairs can become so tiring. As bothersome as physical weariness can be, it is not the only kind of weariness.
People can grow mentally weary or emotionally weary, but the worst weariness is spiritual weariness.
This weariness affects young and old alike. We are sinners. If we take God's Law seriously, we know that our sin deserves God's punishment. Anyone who tries to get right with God by following his Law will soon grow weary. Yet so many ignore his gracious call.