Description:
If your health drop below 30% in combat then a slow time effect will activate. The slow time effect will last for 500 seconds or until your health is over 25% or you're out of combat. The slow time effect will have the same strength as the first shout of Slow Time.

The Fight or Flight ability will be added to you when you first start the mod, so there's no book or quest to get the ability. If you didn't get the Fight or Flight ability then open up the game console and type: Help Fight. Look for the line: SPEL: (XX000D64) 'Fight Or Flight Ability'. Type into the console: Player.AddSpell xx000D64. Replace the two xx with what you see in your game console

I didn't add any pictures becuase that wouldn't help demonstrate the slow time effect, so here's a pic of my Lydia.

Install/Uninstall

For a easy install and unstall use NMM for the mod.

For a manual install unzip the Fight_Or_Flight archive file and drag all content into your skyrim data folder.

For a manual uninstall delete these files inside your skyrim data folder:

Data\Fight_Or_Flight.esp
Data\Fight_Or_Flight.bsa

Credits:
Bethesda Skyrim/Creation Kit
Nexusmods Skyrim
Skyrim Modding community

Requires:
Latest Skyrim patch 1.9

1.01
Health threshold increase from 25% to 30% before slow effect starts
Fixed and removed reduntant codes in script