The 1% rule
Never risk more than 1% of your account on a single trade. With $10K, max loss per trade is $100. A string of 10 losses takes you down 10% — survivable. Risk 5% and the same string wipes you out.
Sizing follows the stop
Decide stop level first, then size to risk budget. Position size = (account × risk%) ÷ (stop distance × pip value). Never adjust the stop to fit a position you wanted.
Stops, slippage, gaps
Stops aren't magic. Fast moves cause slippage. Weekend gaps are real. NFP/FOMC widens spreads — a 10-pip stop can become a 25-pip fill. Size for the worst case.