The ability to "turn it on" and "turn it off" again is sometimes called "Killer Instinct". This intense shift from calm to storm and back again is the one skill that makes all the others effective in a life and death struggle. It is the missing element in almost every "technique based" approach to personal defense. It happens to also be a keystone in the approach taken by A Personal Defense.
Now that I think of it, that's part of why I love the Bourne movies and TAKEN with Liam Neeson so much. The main character never freezes, never panics, and yet when the time comes to turn on the heat, he can do it without going crazy. Big props to Mick Gould (Former SAS and Technical adviser for TAKEN) and Jeff Imada (Student of Dan Inosanto and fight choreographer for the Bourne movies)!
You can train this ability a bit next time you stub your toe or get cut off in traffic. When you feel the adrenaline flow, channel it. Breathe deeply into it. The biological reaction is still there, but your emotions are in check. You are in control, and that's how it should be.