A 70% win rate over 10 trades tells you almost nothing; over 300 trades it is meaningful. Randomness alone produces long streaks, so judging a strategy or yourself on a handful of trades leads to abandoning good approaches and keeping bad ones.
Most traders should think in blocks of 20 to 50 trades before evaluating a change, and in hundreds before trusting a number.
Example: a coin with a true 50% hit rate will land 7 or more heads out of 10 about 17% of the time. A strategy that looks 70% over ten trades may be a coin.
Related: expectancy, win-rate, backtesting, gamblers-fallacy