Quote Originally Posted by Greedo017
"If you bet so little that it's +EV for your opponent to call, then it's -EV for you... Poker is a zero sum game..."

that's not exactly true. If the pot is 14 million dollars and you have 1 dollar left, even if a flush scare card hits and threatens your set, if your opponent puts you all-in for your dollar on the river, it is +EV for him to put you all-in with a flush, and +EV for you to call with your set, because odds are greater than 1 in 14 million that your hand is actually good.
Even when two player play a hand perfectly, and both are making what baised on incomplete information appears to be a +EV move, they are not.

When talking about "Zero Sum" you need to look at the actual cards and odds that each person has...

To put it another way, if you have a set of 999 against someone with a set of 555, and they make a pot size bet, they think it's a +EV move, and you think it's +EV to call.

But in fact it's -EV for him, and +EV for you.

If he had TTT, then you would still think that your making a +EV move, but now it's a -EV move.

Zero Sum is talking about the actual cards in play, not the cards that you think he has.

In The Theory of Poker Sklansky identifies poker's fundamental theorem, which (paraphrased) states: you have made a mistake when you didn't play the same way that you would have had you seen your opponent's cards. Your opponents make a mistake when they do likewise.