This, I believe

Hold yourself responsible for a higher standard than anyone else expects of you.
Never excuse yourself.

Henry Ward Beecher

We are what we repeatedly do. Excellence, therefore,
is not an act but a habit.
Aristotle

You cannot plough a field by
turning it over in your mind.
Author Unknown

Nothing will ever be attempted if all possible objections must first be overcome.
Samuel Johnson

Knowing is not enough; we must apply.
Willing is not enough; we must do.
Johann Wolfgang von Goethe  

Nothing great was ever achieved without enthusiasm.
Ralph Waldo Emerson

Self-trust is the first secret of success.
Ralph Waldo Emerson

Genius begins great works; labor alone finishes them.
Joseph Joubert

Half of the failures in life come from pulling one's horse when he is leaping.
Thomas Hood

It is the want of diligence, rather than the want of means, that causes most failures.
Alfred Mercier

You will never "find" time for anything. If you want time, you must make it.
Charles Bruxton

I recommend you take care of the minutes and the hours will take care of themselves.
Earl of Chesterfield

They can because they think they can.
Virgil

Keep steadily before you the fact that all true success depends at last upon yourself.
Theodore T. Hunger

Success is the sum of small efforts, repeated day in and day out.
Robert Collier

He who would do some great thing in this short life, must apply himself to the work with such a concentration of his forces as to the idle spectators, who live only to amuse themselves, looks like insanity.
John Foster

It does not matter how slowly you go so long as you do not stop.
Confucius 

I cannot give you the formula for success, but I can give you the formula for failure--which is:
Try to please everybody.
Herbert Bayard Swope

If you wish success in life, make perseverance your bosom friend, experience your wise counselor, caution your elder brother, and hope your guardian genius.
Jospeph Addison

(Quotes from http://www.inspirational-quotes.info/)