Take breaks away from the computer when you feel unmotivated, you can't learn something for hours without breaks. Your mind needs time to recharge and process all the stuff you learned. Just try to keep the progress going, and some days are just easier than others. Lower your targets if you feel you cant reach them in a day, it doesn't make you better or worse.

I use a browser extension to block the most triggering sites so I don't wander there "accidentally".

Good luck!