What is a stop-loss?

A stop-loss is not a guarantee of an exact exit price. In a fast or illiquid market, slippage can make the fill worse than the trigger. It is still useful because it defines the point where you stop paying for a wrong idea.

Place a stop where the trade thesis is invalid, not at a random distance that makes the position size convenient. Then size the position so the loss at that level is acceptable.

Moving a stop farther away to avoid taking a loss changes the original risk. If the market moves against the idea, protect the account before protecting your pride.