I want to block some sites(e.g. youtube,news sites ), because I have a problem with procrastination and I find these websites affect my productivity very much. I used to block them by adding them to HOSTS file. However, gradually every time I want to take a break, I open the hosts file and comment my block again. Is there any way I can block the websites and cannot (at least a little bit hard, e.g. I have to reboot my pc) unblock them. I have no access to the router or any firewall, besides the ones on my computer. I just want to FORCE myself to work without any chance to procrastinate.