Not exactly a quote , I have this posted on a magnet on my fridge and recite it first thing every morning - I just change the 2nd person you or your to the 1st person I or my.

Promise Yourself

To be so strong that nothing can disturb your peace of mind.
To talk health,happiness and prosperity to every person you meet.
To make all your friends feel that there is something in them.
To think only of the best.
To be just as enthusiastic about the success of others as you are about your own.
To forget the mistakes of the past and press on the greater achievements of the future.
To wear a cheerful countenance at all times and give every living creature you meet a smile.
To give so much time to the improvement of yourself that you have no time to criticize others.
To be too large for worry,too noble for anger,too strong for fear,and too happy to permit the presence of trouble.

Christian D Larson.

I have not failed. I've just found 10,000 ways that won't work.

Thomas A. Edison

"Be the change you want to see in the world." Mahatma Gandhi

Love this one:

The optimist sees the rose and not its thorns; the pessimist stares at the thorns, oblivious to the rose - Kahlil Gibran

I used this quote in a question before, and this may sound like a negative advice but it really isn't. It is a wonderful expression of the mechanics of attraction in a nutshell. (I got it from the Connecting Link magazine)

You are always, always, always in abundance.

However, If you definition of that abundance is limited

Then limitation is the form of your abundance.

I AM CREATED UNIQUELY LIKE A DIAMOND TO SPARKLE EVERY DAY

What the mind can conceive and believe, it can achieve. - Napoleon Hill

I have always liked this one:

"Where there's a will, there's a way."

Short and inspiring: “The man with courage is never afraid!”