I'm assuming this is a phone and you get most of your screentime at home. Start making it inconvenient for yourself. Set a really long password and disable biometrics. Uninstall interesting apps. If you can, block any sites taking up your time at a DNS level. Keep chargers away from places you can settle like couches or bed; use a very short cord or finding places you'd have to stand to charge it. Find replacements like books, physical things like legos or art. These are all just ways to start.