Here's a way I think about trading which helps me to "do the right thing" when it counts. There are two faucets in front of you. One is colored green, the other red. Unlike a normal faucet, either fresh drinking water or sulfuric acid can come out when you turn it on. You never really know which one it will be. However, whatever comes out of the green faucet, the other thing comes out of the red. The water pressure (or acid pressure) varies. You can open the spigot all the way and it may come gushing out, or it may just drip. Also, the liquids many times change back and forth while the faucet is open. Sometimes they do so gradually, other times very quickly. The only thing you can control is the spigot and of course you can choose which faucet to open.