How do I enable the Health Shield (iOS)?

As a Duolingo Plus subscriber, you have the option of enabling the Health shield. This way, you won't lose Health bars for an incorrect answer while in a lesson. To turn on the shield, follow these easy steps: 

1. Make sure you have the latest Duolingo app version.
2. Open your Duolingo app and tap on the "Health" tab (it's the second icon from the left at the bottom of your screen).
3. Enable the "Plus Health shield" by tapping on the toggle button.
4. Now you should be able to make mistakes without losing any health.