Found these quotes while surfing the net: here.

Now we are getting to that top.  Taking a closer look at 1 through 4, gives some concise lessons on the game.

1. David Sklansky on Poker

“When we play, we must realize, before anything else, that we are out to make money.”
 
Some people play for fun, some people play to socialize, but for those few of us that play for a living this is the sentiment that should echo in our brains.  You play to make money.  You play to win.  Every decision should be done to be the most profitable long run. Whether it’s live or internet poker, there is only one goal.   Sometimes we forget this.  Sure experiment with your game, but always try and win money. 
 
2. From Big Deal by Anthony Holden
 
“Poker may be a branch of psychological warfare, an art form or indeed a way of life – but it is also merely a game, in which money is simply the means of keeping score.”
Mr. Holden’s book is great read, and though money is the way to keep score, he’d do well to follow Sklansky’s quote above.  Of course Holden’s sentiment is a little more sublte.  Life is kept score with money too.  Still, poker is a game and player’s shouldn’t see it for something more than it is.  It’s still a game, even if you are playing to win money, you are still playing a game.

3. David Mamet on Poker

“Poker reveals to the frank observer something else of import—it will teach him about his own nature. Many bad players do not improve because the cannot bear self-knowledge.”

Self-knowledge is a painful lesson for many.  Ego gets in the way, being too close to the subject of inspection (or introspection more accurately), but poker as tool for improvement and self-actualization is a powerful thing.  It’s not to be underestimated. 

4. Bobby Baldwin on Poker

“You cannot survive without that intangible quality we call heart. The mark of a top player is not how much he wins when he is winning but how he handles his losses. If you win for thirty days in a row, that makes no difference if on the thirty-first you have a bad night, go crazy, and throw it all away.”

Very similar to Pug Pearson’s quote.  It’s an important sentiment.  Some players can throw years worth of work away in one night.  The guys like Baldwin who have been through it all can see in retrospect just how hard the temptation of self-destruction is when things aren’t going your way.