You're always gonna be blessed with the people who try to bring you down... try to tell you that you can't do something. I say 'blessed', because it's true! Without those people, who would be your motivators? In every aspect in life, prove the disbelievers wrong. The bullies, the haters, the negative Nancys, and the miserable Melvins... Prove them all wrong.
When you think you can do something, that means you CAN do it. If you push yourself hard enough, and you tell yourself that you can, you will... With no doubt about it.
Have a mess up? Learn from it. Get back up, and learn from the experience. Recovering from an eating disorder? Have people doubting you can do it? Prove to those people who think you're never gonna recover wrong. Let the haters be your motivators and nothing more. Feel like giving up? Don't. Why? Because there are people who are waiting for you to give up. There are people who would kill to see you fall. Prove 'em wrong. Every single one of them.
Live freely, stay positive, and most importantly; keep pushing. The moment someone tells you that you can't do something, that's a sign you must prove them wrong.