Leechblock(Firefox add-on) did the job for me; you can make the websites available only for some amount of time per day/week and then they'll be blocked. The ef

Leechblock(Firefox add-on) did the job for me; you can make the websites available only for some amount of time per day/week and then they'll be blocked. The effect of this after a while was that I lost interest on reading news endlessly. In the general case, I think that first you need some tools that force you to change your behaviour; after a while it becomes a habit and you won't need then anymore.