Set time aside when you are allowed to do it. In other times block the offending sites completely. Ask yourself a question - is what I am doing right not benef

Set time aside when you are allowed to do it. In other times block the offending sites completely. Ask yourself a question - is what I am doing right not benefitting me in a way a walk/exercise/spending time with family/doing practical coding/starting a business/insert your favourite would? If now, stop and move on. Why it's not easy? Because it's a habit which has its own trigger (sitting at a computer). Unfortunately as a developer you cannot get rid of the trigger. From own perspective - rearranging the work space or changing helps for a while and then slowly you fall back to old habits, so I wouldn't say it's a permanent solution.