Money is important. Time is important. But these are not the quantities that will limit you in your life.

Without energy, neither of these factors means very much; nothing really does. Think about it: you could have a huge bank account, but it won’t matter one bit if you’re confined to your bed with glandular fever and unable to stand up straight, let alone spend and enjoy that money. You could be young, bright, and full of promise, but if you’re depressed and lethargic one hundred percent of the time, all that youth and potential mean nothing. Without energy and the capacity for action and execution, all your best intentions won’t matter a lick.

This is a book about the psychological and physiological bases of energy—where it comes from, how we can maintain it, and how to get more of it. You can think of energy as the most primordial, fundamental kind of wealth. Energy—whether it’s psychological or physical—is like your personal fund of life itself. It’s the well that you draw all your motivation, enthusiasm, and passion from. It’s what makes one person’s life a boring slog while another person, doing much the same thing, appears to be living with zest and purpose.

It all comes down to energy. There’s a great big world out there, and if we’re to explore it, we need the physical and emotional strength to get out there and engage with it. Opportunities abound all around us, but if we’re too depleted and uninspired to grab them when they do, it doesn’t matter how fortunate we are or how many lucky breaks come our way.

It’s a little like having the world at your feet and a map of this world’s awesome highways and roads in front of you, but not having any fuel in your car. Without energy, life becomes two-dimensional and gray. You may even feel like life is just whizzing past you, and you’re left behind because you can’t keep up.

When we have energy, the world is ours. We have the spirit and the wherewithal to grasp it. We can reach out and engage with others, with our environment, with ourselves, with our dreams. We have what’s needed to build our ideal world one brick at a time, and we have the resilience and spring in our step to appreciate what we already have.