How you handle periods when capital is shrinking – this defines a trader's career.
Example
Your account grows from €10,000 to €12,000, then falls back to €9,000. Your drawdown is not 10% (from the start) but 25% — measured from the high (€12,000) to the low (€9,000). Crucially, after a 25% drawdown you already need +33% just to get back to the high. This asymmetry makes drawdown control more important than chasing gains — and it is why prop firms like FTMO enforce hard drawdown limits.