Imagine a man named Mark. Mark is 48 years old, and lately, he feels like a shell of his former self. Every day around 3:00 PM, he hits a "wall" of exhaustion that feels like swimming through deep mud. His "brain fog" makes it hard to focus at work, and he has completely lost the "spark" for his hobbies and his relationships. He is tired, moody, and just wants to nap.