A stop loss is the point where your reason for being in a trade no longer holds. It gives risk a boundary before emotions get involved.

Set the stop from market structure or your setup rules, then calculate position size from that distance. Do not place it only where a dollar amount feels comfortable, then move it when price approaches.

A stop does not guarantee an exact fill in volatile conditions. It does make the decision explicit. Combine it with a planned risk-reward ratio before entry.