I've discussed before, there's several options one could consider and can be influenced by your risk tolerance, trading style, and charts/triggers you are looking at

1. one option is to just stop out at the STS price and that's it. That stats are generally a bit better that way
2. another option is to stop out at the STS price, and if price ends up rallying back off the lows that day and closes back above the STS add the position back
3. another option some people like to do is wait for the close - that avoids some whipsaws but it also doesn't protect you on days when the STS might have gotten you out in the morning when SPX is only down 10 points but ends up being one of those days when the market crashes and SPX ends up down 140 points -waiting for the close on those situations you give a lot back vs just exiting at the STS