If you're about to die in Survival mode, press the Home button on your device to be brought out to the menu. Tap the main menu twice to bring up programs in memory and close the Street fighter program by holding 2-3secs on the icon. Once the game is closed, re-open the street fighter game again to see that your amount of energy is back to what it was at the start of the match. If done correctly you can have unlimited matches in survival mode.