When saving/logging a session, you can deactivate the "Share note" button. By disabling not even your friends will see your note. You can deactivate or activate the "Share note" for each individual session. Go to Stats > Click on Sessions (the first row) and then tap on any session to edit and adjust this setting. When the "Share note" button is enabled, your note will appear on the Public feed as well on the Friend feed.
If you don't even want to share that you have meditated, you can deactivate the "Public feed" under "General Settings" on the Settings screen.
Please keep in mind that ZenFriend is a worldwide meditation community that encourages each other by sharing their sessions, so we recommend to deactivate the public feed only when absolutely necessary.