Virtually every poker situation can be broken down to a simple mathematical formula. If there is $600 in a pot and you bet $600, you’ll be getting even money on your proposition. That means, in the long run, you’d have to win that pot half the time to make it a profitable play. When you consider that the hand will play out almost identically with a $400 bet, you’ll see that, mathematically, it often makes sense to choose the smaller bet. [...]
You will rarely see a to professional bet all of what’s in the pot when you watch poker on television. They’ll vary their bets generally between one-third, one-half, and three-quarters of the pot. They understand that by keeping the pots smaller, they’ll have more control over the outcome. And that’s just what they want – to maintain control of the table.

Daniel Negreanu – 01/2007 – in Hold’em Wisdom for all Players