Basically just use 2% of your entire portfolio for trading and you're safe, on top of that you don't use all of that 2% but just few percent of it if you future trades.
It's simple and basic money management that people often overlook but can save them from losing in the long run.

Too bad though most of people will ignore such advice and just going into trading thinking they're the chosen one and gonna become the best trader in the entire world.