You're reduced to gross motor skills, your will not be rational, and you face danger, you will either do the following:
1. Fight
2. Flight
3, Freeze
4. Faint
It depends on the level of heart rate. At a certain rate ,you will experience peak of your combat performance. You will at that rate, be faster, stronger, and focused.
At worst, you will flee, freeze, or faint. But this can be mitigated because it depends on your training. If you are well trained in combat, you will fight, but if not, you will react in the three others,
It's nothing to be ashamed of, it's a survival mechanism.
http://www.crisisresponse.org/uploadedFiles/06%20-%20Heart%20Rate(2).pdf