I came across an article The Ultimate Math Guide For Traders on Tradeciety website which every serious trader should know by heart.

I see so many posts about being right and wrong about one position, but hardly any on the impact of traders

If you don't know your systems Win rate expectation (from your past 100 trades taken), you don't know which potential trades meet your risk reward ratio goal that puts you in the green field and which do not and thereby should be passed. Trading is a game of statistical probabilities and not about being right or wrong. Being right on wrong trades, will not make you profitable trader.

Combined with

I see so many posts about being right and wrong about one position, but hardly any on the impact of traders

**Win Rate VS. Risk Reward ratio**correlation to traders success or failure.If you don't know your systems Win rate expectation (from your past 100 trades taken), you don't know which potential trades meet your risk reward ratio goal that puts you in the green field and which do not and thereby should be passed. Trading is a game of statistical probabilities and not about being right or wrong. Being right on wrong trades, will not make you profitable trader.

Combined with

**proper position sizing**it is single most important thing to understand, if you want to become a profitable trader. You must play small on one position to allow statistical edge of your trading system to work for you. If you make big bets every single trade, you are gambling, not trading. You may get lucky and get rich quickly, but you will more probably go broke.