To permanently delete your account, go to this page. https://www.facebook.com/help/delete_account

Facebook uses psychology and desperation to try and prevent you from quitting.

If you plan to detach yourself and use self-control to "quit" Facebook, here are some tips:

Opt-out their email notifications.

Make your profile less visible by making your timeline, photos, and anything else you can, private.

Delete the app from your phone.