To many, Dan Hegarty's experience of hitting his forties will sound depressingly familiar: he was tired, irritable, his body ached and he had lost his joie de vivre. "Every afternoon, I would have a lull in my energy levels," he says. "My concentration wasn't as good as it used to be - I couldn't even concentrate on a newspaper. I wasn't sleeping so well, and my libido had dropped off."
