As a Duolingo Plus subscriber, you have the option of enabling Unlimited Hearts. This way, you won't lose Hearts for an incorrect answer while in a lesson. To turn on Unlimited Hearts, follow these easy steps:
1. Make sure you have the latest Duolingo app version.
2. Open your Duolingo app and tap on the "Hearts" tab.
3. Tap the Unlimited Plus.
4. Now you should be able to make mistakes without losing any health.
Note: you can also turn on Unlimited Hearts by tapping the Plus badge.