There is no switch, you likely need to do a restore on the phone as something is corrupt. There may also be an issue big enough where you have to totally re-load the default ROM using a computer.
It goes to that mode when it can't load the regular system, you can't just tell it to stop without fixing the issue that is causing it to do that. For a device like a phone you'd have to restore it to factory defaults which will wipe the internal storage.