If you are trading without a stop, you are playing with fire. Not because the market can move 100 ticks in a second — though it could. But because then, you haven't clearly defined your risk. And without doing that, you are likely to let your market bias keep you in a trade longer than you should be... increasing losses.
That is the kiss of death.
Just because you should have a stop doesn't mean that all stops are created equal. There are three main ways to set a stop: (1) financial — based on the amount of money that you are willing to lose; (2) static — your stops are the same for every trade; and (3) technical — you use market information to tell you when your thesis is proven wrong. Here are the pros and cons to each.