The more sophisticated you become as a trader, the more you will realize that trading is completely mental. It isn’t you against the markets, it’s just you. All the other traders participating to make the market provide you with an opportunity to make money from their divergent beliefs about the future. If people didn’t disagree about the future value of any particular commodity or stock, then there would be nothing to compel them to either bid a price higher or offer it lower, and the opportunity to profit from these changes would cease to exist. So the markets just offer the individual trader opportunity.
– Mark Douglas, The Disciplined Trader