It is good to know that when you leave Family Sharing, your Apple ID is removed from the family group. That means you will lose access to any services shared by your family. Moreover, any DRM-protected music, movies, TV shows, books, or apps that you previously downloaded from other family member's collections will no longer be usable.
In order to turn the things off, follow the steps below:
1. Open Settings.
2. At the top of the screen select your name. Tap Family Sharing*.
*Users of iOS 10.2 or earlier should go to iCloud > Family.
3. Tap your name again > select Stop Family Sharing.
4. Confirm the action by tapping Stop Sharing.
Note: When the family organizer turns off Family Sharing, all family members are removed from the family group at once. If there are children under 13 in your family group, you must transfer them to another family before you can disable yours.
Now, you share the apps only with yourself :) Enjoy!