A 61.8% line is not automatically a stop, and crossing it does not automatically reverse the market. Invalidation belongs to the setup you wrote.
Separate three different failures
First, the expected reaction may never appear. That invalidates an entry trigger, even if the wider trend survives. Second, price may break the structural swing supporting the retracement. Third, your allowed risk may be too small for the technically logical stop. In that case, the trade is unsuitable even though the analysis may remain plausible.
Write it as an event
“Below Fibonacci” is vague. “A 15-minute close below the impulse origin” or “failure to reclaim the broken range before the session ends” can be observed and reviewed.
Before replaying a chart, complete this sentence:
I will abandon this setup if ________, because that would contradict ________.
The second blank matters. It connects the invalidation to the original evidence instead of an arbitrary loss tolerance.