Learn to love it and you'll keep doing it

Here's a question people ask me: "How do you stay motivated to keep going and keep working out even when you really don't want to?"

Most people struggle with motivation every day. I'm one of them. Motivation can be broken down into a few subcategories. My fifth Law of Health and Fitness is "Loving It." Progress and motivation are possible if you look forward to your workouts. They have to be challenging and interesting to you. If you despise them before you start them, you're not going to survive them for very long. If your reasons why are meaningful to you, then staying motivated is easier. I'm always promoting health, fitness, quality of life, and feeling good as reasons to get and stay motivated. Not to say that a person's goal to lose weight or fit into smaller clothes isn't motivating—it's just that when these goals are obtained then new ones need to come into play.

When the numbers on your scale and measuring tape are low enough to make you happy then it's important to start to explore some new numbers. I'm talking about numbers that relate to ability, improvement, and achievement. Your physical appearance will improve at a more rapid rate if you can start to exercise with your focus on power, speed, and strength. This mind set applies to both men and women. This means that your motivation comes from your desire to work hard during exercise at home and out in the world. Let your workouts trigger something new and bigger than anything you've done before. For me it's improving my run times or completing something new. For you it could be anything that pushes you beyond the confines of repeating the same workouts the same way, day after day.
(some of this information was provided by by Tony Horton, creator of P90X)