You gain back one exertion for each Very Fast action you don't take, Burn (though being exerted burns up your main action anyway so you cannot reclaim exerion on a skipped action).
Well, that is something you can be doing in the meanwhile, Fire...
"Err... Cloud's in a bit of trouble," she says. "Mors and Heph are dodgy but holding. You still have to fight through to the stairs on the other end of this floor; you have some better quipped guys waiting for you there. And that helicopter is nearly powered up now!"