You are your greatest challenge.
You can out run someone stronger. You can out smart someone faster. You can even out lift someone smarter. But you, however are your greatest opponent. How do you beat someone who knows your next move? How do you defeat someone who knows how long you can go? How can you finish before someone who knows your weaknesses? Who has all the same characteristics. You can't. Only you can defeat yourself. You are, and forever will be your greatest obstacle.
The only way to defeat you is if you were the new you.
That's why you must Be the New You everyday , being better than the last you.