You didn't have a stop in place?  It gapped down below Friday's low after cutting guidance - one must have a PLAN in place that includes an EXIT STRATEGY.   Today's news was pre-market and gave you time to act.  Get away from using stop limits unless you can react to news.   This is simply a trading stock and I'm certainly not familiar with their fundamentals and would have exited stage left on that news.  Understand, we cannot provide direct trading advice so you must adhere to your plan.   This will be another item to discuss in the educational examples - although rare,  pre-announcements can be good or bad ahead of earnings.   Lastly, with a plan you avoid having to make decisions of what to do like today - you already have the exit in place and simply adhere to your plan and accept the outcome.  Sometimes we get a positive surprise and other times a negative headline - it's part of trading.