Your environment influences you a lot more than motivation or willpower
Motivation feels amazing. It makes you feel on top of the world for some time. But it is also very easy to lose it the next day.
I can't say talk about everyone's willpower. But it is incredibly hard for me to use willpower for everything.
So don't just rely on motivation, willpower, etc. Use your environment for your benefit.
Make it easier for you to do what you want to do rather than what you don't want to do.
Change your environment to create as much friction as possible.
Internet
I think internet addiction is basically a prerequisite of PA.
Think of the internet as a tool.
Think of the internet as a tool you use to connect to different people.
Visit these subreddits if to tackle IA(Internet Addiction) r/nosurf, r/digitalminimalism, etc.
Consider a cheaper internet plan.
Learn a new non-digital hobby.
Make it harder generally to use internet
Don't sign in everywhere with your accounts.
Use locks, passwords.
Try to download and watch things.
Make it easy to
Device
Blocker
Remove/Delete content.
Put restrictions
Don't bring them everywhere if not needed.
Room
Put your phone in a different room when sleeping.
Clean and organize your room.
Try to keep your room door open if possible.
Sit in your living room or go to a coffee shop while using a computer.
Open your curtains.
Relationships
Call your friends.
Call your parents.
Invite your friends to your home or go to their home.
Promise to play an online game with your friends.
Have more encouraging/positive friends if possible.
This is only for some teenagers. Try to reduce talking about porn, pornstars, getting girls, etc. if you do.
Generic
Try bright-colored clothes or objects.
Do things you love.