What happened? Facebook happened. Email happened. Internet in general happened.
I personally think if you require a feature to keep yourself from wasting time, and become responsible, then you have more important things to worry about, and bigger problems.
This is exactly what I was about to post. No offense to the OP or anything here I don't mean to call you out specifically just anyone in general with this issue. I mean, what ever happened to our society's self-control? Think about it for a minute: do you really need the feature that blocks the forum so you can do work instead? If you can't just put your head down and get to work when it's necessary, then life is going to be very difficult for you. If that's really the case, then fixing that issue first needs to be your top priority as I would argue that is more important than learning any language.
These days, there are a million possible distractions all around you. Especially for people working with a computer all day (like me). It's quite easy to say "oh wait, let me check X real quick" and down the rabbit hole you go. Maybe you two are very good at self-control but society in general isn't. We're only human after all! The world around us has conditioned us towards instant gratification, and productivity is paying the price for it. Why do you think there are a gazillion productivity apps, or TODO apps out there? Because people need them. Plain and simple. Procrastination is an issue nowadays. Not for everyone, but for a whole lot of people, for sure.
One of the reasons this affects some more than others is just age, job situation etc. If you're middle-aged, have a family and have a full time job, i don't expect procrastination to be an issue really, simply because you got a lot to do (real obligations) and so little time. So you just do it. You go to your job, and when you get home you do stuff with your family. You also remember a time before computers/internet, so you might not use a lot of its possible functions.
Now imagine a student in his college dorm. Heck, let's take me as an example. I grew up with the internet and if i wanted to, i could go a whole day without barely leaving my desk, because everything is digital nowadays. I learn new things, read, watch TV, and chat with friends, all on my computer. Besides classes, i don't really have any obligations. So there is a whole lot of things i could potentially do, but being human, i often follow the path of least resistance. That's indeed sad if you don't experience this issue, but it's the ugly truth and more common then you would imagine. Instead rejoice we want to do something about it.
(the above paragraph is an example, not an assumption about any person here)
I really don't think age has anything to do with it. I'm 29 years old - I remember a time before computers were commonplace (when I was a child) and I remember a time when my dad would come home and tell me stories about how he "surfed the internet at work today." Having said that, I was still in college less than six years ago and continued going to school after receiving my bachelor's degree as little as a year ago. I don't think that age or generational gaps have anything to do with self-control.
Believe me, I'm just as susceptible to distractions as you - I LOVE to play games on my phone or 3DS or one of the many handhelds for general emulation I've purchased throughout the years. The difference then is not that I'm able to focus because today's technology is so much more commonplace (because it was commonplace when I was in high school and college as well) - it's that I use my self-control to not allow that technology to interfere with real obligations when necessary. That comes down to self-restraint and (as you suggested) maybe it's that I have more than you. I don't know. But I really feel like creating an add-on that allows you to disable the forums, which you can then re-enable whenever you want, is just not a proper solution. If you can re-enable it at any time, the temptation will still be there when it's disabled. If you're able to say "Well, I'll just use self-control to NOT enable it until I'm done with my reviews" then why can't you apply that same self-control without the add-on to not scroll down to the forums before you finish your reviews as well?
Don't get me wrong, this isn't meant to be some lecture about how "this script is pointless so don't make it!" or anything. If the script helps then use it I guess - I just can't logically work out how this add-on is necessary for anyone. If the add-on permanently switched the forums off until it could tell that you'd finished your quota for reviews, then it would make perfect logical sense. But since it's still up to the user to enable/disable the thing, it's nothing more than a placebo. And it doesn't even have the benefit of the actual placebo effect either.