When you take a fatal hit in Borderlands 2 you can revive if you get a kill before the countdown timer expires.
Kill an enemy to save your life and get a second wind.
Get a kill to revive.
Note that if you've recently recovered from Fight For Your Life mode, be careful - if you fall into Fight For Your Life again, you'll have much less time to get your Second Wind!
You can move while in Fight For Your Life mode.
