One of the things that most helped me was school forcing me away from my phone or the library. Best to find something that will force you to be productive away from your phone.
If it's not with other people the first few days of complete separation will be unproductive and painful and distracted. But once you force yourself to work for a few hours... You'll get more and more into it. Let me know if you want a VC coworking session hehe
