What do you think of this quote concerning trading

Remember, trading isn't about understanding what's true, but understanding what most other traders are thinking.

A friend said this, but I strongly disagree with this quote. It is that mentality that won't get you ahead in trading. Of course, you can have a feeling what the herd will do. But you got to have a little bit of back bone and make a decision based on supply and demand. This is the only way of thinking that will separate this form of activity to gambling, in the form of say poker. If you want to play poker, play. But if you want to participate in the financial markets, think big! It may be a gamble, but it will surely be rewarding.