Remember: Futures Trading is Zero-Sum
For every trader betting on higher prices, another is betting on lower prices. These trades are matched. In the stock market, all investors (buyers and sellers) can profit in a rising market, and all can lose in a falling market. In futures markets, one trader's gain is another's loss.
In the world of futures speculation for every long there is an equal and opposite short. That is, unlike the world of equity trading where there needn't be equal numbers of longs vs. shorts, in the world of futures dealing there is. Money is neither made, nor lost, in futures; it is simply moved from one pocket to the next as margins are swapped at the close of trading each day. Thus, every time there is a buyer betting that prices shall rise in the future, there is an equal seller taking the very opposite "bet," betting that prices will fall.
~Dennis Gartman, in "The Gartman Letter"