Even though it based on probability it's doesn't mean that everything is based on probability, if you study the market very well you will increase the chances of gaining and not loosing.
There's some things that have to be observed before trading, someone can't just go into trading because they said it based on probability the person will eventually loose everything.
Before you go into trading do the following
Study the market very well
Gather informations and knowledge on trading
Take a step at a time