I have also been trying to slow down and it has had a profound effect on my overal performance and happiness. I think cutting out youtube and hacker news is a bit much though.
HN has perhaps had the least impact on my productivity of any site I've been addicted to. HN's procrast setting makes the addiction quite manageable in fact. If you set the timeout to integer hours between 5 minute blocks lost productivity is minimized.
What I find is I'll open ~5 comment sections, read, then leave for 2 hours. By the time I get back a significant portion of links have been replaced. Rinse and repeat. The key mechanism is the timeout forces me to break out of zombie reading and refocus on programming.
I would encourage anyone with a self-diagnosed HN addiction to turn on procrast.