The faculty of voluntarily bringing back a wandering attention, over and over again, is the very root of judgment, character, and will.  No one is compos sui [master of himself] if he have it not.  An education which should improve this faculty would be the education par excellence. But it is easier to define this ideal than to give practical directions for bringing it about.
~William James, The Principles of Psychology, 1890.

When you write down your ideas you automatically focus your full attention on them. Few if any of us can write one thought and think another at the same time. Thus a pencil and paper make excellent concentration tools.
~Michael Leboeuf

The five essential entrepreneurial skills for success are concentration, discrimination, organization, innovation and communication.
~Michael Faraday

The true art of memory is the art of attention.
~Samuel Johnson

Concentration is the secret of strength.
~Ralph Waldo Emerson

Nothing interferes with my concentration. You could put on an orgy in my office and I wouldn’t look up. Well, maybe once.
~Isaac Asimov

Ninety percent of my game is mental. It’s my concentration that has gotten me this far.
~Chris Evert

Concentration and mental toughness are the margins of victory.
~Bill Russell

Discipline and concentration are a matter of being interested.
~Tom Kite

When meditation is mastered, the mind is unwavering like the flame of a lamp in a windless place.
~Bhagavad Gita

Throughout my career, if I have done anything,  I have paid attention to every note and every word I sing–if I respect the song.  If I cannot project this to a listener, I fail.
~Frank Sinatra

Give whatever you do and whoever you are with the gift of your attention.
~Jim Rohn