How do you establish a no-tech-distractions policy?

I can relate to your experience. However, I struggle with keeping digital entertainment away from me. On good days, I keep away from entertainment until I'm done with work. On unproductive days, I start one thing piece of entertainment and collapse through a series of distractions. It's like, I start with Instagram, find myself on reddit, then on Youtube, then on Netflix, then on porn. I have this problem of the dopamine train which I unwillingly get on. Can you offer some advice?