You cannot perform in a ...

You cannot perform in a manner inconsistent with the way you see yourself.
You cannot perform in a manner inconsistent with the way you see yourself.

More phrases

Don't settle in the land of barely enough. That is where you are, it is not who you are. That's your location, it's not your identity. No matter what it looks like, have an abundant mentality.
The by-product is that they more people you help, the "richer" you become, mentally, emotionally, spiritually, and definitely financially.
 T. Harv Eker
Happiness doesn't depend on any external conditions, it is governed by our mental attitude.
The truth is incontrovertible. Malice may attack it, ignorance may deride it, but in the end, there it is.
To improve is to change; to be perfect is to change often.

Quotes from the same author

Your attitude, not your aptitude, will determine your altitude.
You are the only person on earth who can use your ability.
Remember that failure is an event, not a person.
Positive thinking will let you do everything better than negative thinking will.
What you get by achieving your goals is not as important as what you become by achieving your goals.