How do I remove myself from Family Sharing on iPhone?

Have a look at the steps in this related article:

How to leave or remove a member from a Family Sharing group - Apple Support

On your iPhone, iPad, or iPod touch

1. Go to Settings.

2. Tap Family. If you don't see Family, tap your name, then tap Family Sharing. 

3. Tap your name.

4. Tap Stop Using Family Sharing.

Direct link to how to leave --> How to leave or remove a member from a Family Sharing group - Apple Support

It’s ALWAYS best — and will avoid potential “issues” — if one coordinates any contemplated changes w/ the Family Organizer.