For me I had to do science on myself. Keep a journal throughout the day on what you are actually doing, minute by minute. If hacker news is in there too much. Block it (I did this for years=). If you spend too much time polishing and not enough doing, then set alarms for yourself that say "get it working first. Do the core of it." You will find what's slowing you down and then you can take action to fix it.

Also, exercise. Put aside 3 hours a week and run/bike/do anything. It will give you energy in ways you won't expect! You probably are 100% there already, but for me it wasn't obvious and so I wanted to include it.