Is twitter and facebook even important?

[BoB Sir Dylan]

I find myself spending so much, so so much of my free time just browsing down my facebook home and looking on my twitter. I'm 17 now so I don't really use facebook actively (like write status etc.), I only use it to go on messages and message my friends. But I do still go on the home page sometimes and use up hours of my time looking at completely pointless stuff, like funny memes, videos, other peoples popular status's who I don't even know. And also, my facebook seems to be completely crammed with so called 'friends' I have about 900 or something, but I don't know loads of them! The people that are actually my true friends in my year at school don't even use facebook anymore, pretty much my whole year just uses twitter. There's tonnes of random school kids that use it everyday, they're the age I was when I did the same. I've already activated a thing on my google chrome that blocks facebook apart from the messages and my profile page, but when I go on sometimes it doesn't work and I forget about it and end up looking at random stuff for hours on end again.

As for twitter, i use that pretty much everyday. I will write between 1-5 tweets a day I would say. I am following like 170 people and have 215 followers, but like facebook, alot of them are random 'follow back' accounts that post random stuff that is nothing to do with my interests. I would say like 80 of my 'following' are these accounts, so like 90 must be real people I know. I post tweets about myself, and some about general things, and also post lyrics to my favourite rap songs (lil wayne) and videos and funny pictures. Alot of my friends don't even have twitter though. Some people I know use it everyday.

Even the news gets me, I will look for hours at supposedly 'breaking news' articles, but at the end of it, I will have realised I could've spent the time doing productive things for my own benefit (eg. Tidying, revising, going out with my friends) but instead, I just wasted it!

I find it SO hard to understand what IS important and what ISN'T important! The two things get muddled together all the time and I end up putting my studying, family and friends second!

So, are these social websites even important? I'm studying my a-levels at the moment, and I think twitter is okay but facebook is just annoying! What should I do, block them both? Leave one?
It's so hard to stop myself from spending hours on the interent looking at pointless crap! Just to add, recently I lost my brother and best-friend and was diagnosed with aspergers, and under all that hard news I may have been rejecting studying and just spending the time 'in dreamland' if you may, just wondering around on the interent for days and days without a life, and without even noticing it.

(I used to always go on my xbox and play COD: BLACK OPS but I've unplugged it now to help me study)

so the question is, what should I do and how should I do it? What is important and what isn't?