It depends upon the robot. Basically, the way to reduce risk is to keep lot size small. How small? This is where backtesting or testing in a demo account can help. Backtesting, or demo trading for a month or two, will give a good idea of how much is the typical drawdown. From this information you can then determine the lot size you should use.
What robot are you referring too and I can give you an idea of the lot size you should use.
Alan,