Don't put all of your eggs in the same basket
If you divide your forex capital in, say, 50 equal parts, you will never lose more than 2% per trade. If you have three consecutive losing trades, you would still have another 47 profit opportunities left.
That's what they call Risk Management or Money Management. It's easy to explain, and hard to practice.
The thing about 2% risk per trade ... well, it doesn't necessarily have to be 2%. It could be 1% or 5%. The important thing is for you to know at any time after how many more trades will you be out of the forex market, i.e. you must know what the worst case scenario is. It is better to think as a pessimist ('How much could I lose on this trade?') than to start dreaming about your vacation after you quadruple your forex account.
And should we even mention that playing all-or-nothing is lethal to your forex account?