More insight from Jillian Michaels from The Biggest Loser. Can't say it any better.
When it comes to diet and exercise, I forbid you to ever use the phrase: I can't. I'm telling you, there's no such thing! There might be "I don't want tos," but there are absolutely no "I can'ts" from here on out.
Why am I being so hard on you about this? Because I know you can! In fact, I promise that you can do anything you want in this life — if you want it bad enough.
The next time you start to say "I can't," stop yourself and instead say the "antidote" statement, which is "I can." I can lose weight. I can start to exercise. I can get control of my life.
Think about what might be causing you to feel defeated before you even begin, and tackle those negative feelings or memories or harsh life lessons. You have the power to take your life back. Soon you'll see the evidence that you can accomplish your goals, that you are strong and intelligent, and that you deserve everything wonderful that life has to offer. You have nothing to lose and everything to gain, kid!
Do you think you can do it? You can!!