Turn on the system-wide parental controls and have someone else set the password. You can set time limits for apps (x mins per day), designated hours for apps (only between 6-8p), and block apps outright.

If you live with someone who can be your password-holder, this is easy with little downside. If you don't, you need to think about the possibility of emergency use of the phone. But I think it will let you call 911 at any time of day regardless of parental controls.

One thing I will note from when I set this up years ago for a friend's family: there aren't persistent preferences, and once you disable parental controls (even just for a minute), you have to re-enable every single control manually. This may well have changed in the last 5 years though — I certainly hope so!