We can’t control how markets move, so we can’t control whether any single trade we make will be profitable or not. But we can control how we make trades: how we enter, how we size positions, how we exit, and how we contain losses.
Having rules about all of those helps us set specific goals about the process of trading, rather than about the outcome.
The goal of your learning is to trade well, just as the goal of a pitcher is to make a good pitch. If you do that often enough, you’ll win your share of outings.