I've used forest before. Pushing commits feels just as good. I follow a couple pomodoro streamers.. 

The common denominator is, okay, I'll aim to get this or that done today, but if I can set out to work for x hours and do it, that the time itself can be an accomplishment. 

That keeps me going until I hit an actual milestone.  

 But the truth is, if I'm well rested, well fed, well hydrated, working on something I desire, how can I not be productive. 

The gym and the bed are such powerful places. 

Strategic keto/fasting too.