How Apple plans to get you to use your iPhone less with iOS 12

iOS 12 will distract you less
Following on from the Do Not Disturb feature that iOS has had for a few iterations, Apple is now rolling out features to help iOS 12 users to limit the amount of distractions that the apps on their iPhones and iPads (and iPod touch device) generate.
Less distractions at night
The first place that Apple wants to limit distractions is at night. If you need to glance at your device at night, rather than be bombarded by notifications, iOS 12 will keep them hidden until the morning.
Don't worry, all the notifications will be there waiting for you in the morning
Refreshed from a good night's sleep, you'll be ready to deal with all the notifications come the morning.
Smarter Do Not Disturb
iOS 12 will allow you to make smarter use of Do Not Disturb, by scheduling it, and even having it automatically turn off when you leave the current location or the current event ends.
Tired of notifications?
Are you tired of being bombarded by notifications you no longer want to see? iOS has you covered!
Control notifications
Get the option to have notifications from specific apps delivered silently, or choose to turn them off completely.
Grouped notifications
Finally! iOS 12 groups notifications together so you don't have to wade through endless rivers of prompts. Very handy if you find yourself catching up on a group conversation with chatty friends.

Don't worry...
... you can still expend the grouped notifications so you can see what's going on and dive right into things.
Get more information!
How many notifications are you being barraged with? Which apps are the worst offenders? iOS 12 gives you access to this inforamtion and much more.
App Limits
Are there some apps that you find yourself diving into for a few seconds and before you know it you've wasted -- ahem, I mean, spent -- 30 minutes interacting with them? Well, iOS 12 has you covered!
Set pre-defined limits for yourself
Don't worry, nothing is fixed in stone, and if you really need to use the app, you can. But this offers a simple, low profile way to stay in charge of your time.
Notifications put you in charge
Notifications remind you of how much time you've set aside for specific apps.
Downtime
Set a schedule for time away from the screen by limiting you to only apps that you have pre-defined (along with the Phone app).
In control of which apps are always allowed
The idea isn't that iOS 12 takes the control from you, but instead it gives you tools that put you in the control of what you want access to, and what you want to be shielded from in terms of distractions.
Content and Privacy
New in iOS 12 as part of the Screen Time feature are new content and privacy features aimed at putting you in control of both yourself and any kids that use iOS devices.
How much time are your kids spending on the iPhone or iPad?
iOS 12 will give you data on how your kids are making use of their time on the iPhone or iPad. This feature will work across both the iPhone and iPad, and can be set up using Family Sharing and managed from a designated parent device.