Getting into a negative mindset is easy, its getting out thats somewhat dificult. When I was younger I used to have problems kinda like yours. Seeing all the negative things in the world can really bear down on you. A lot of people have mentioned multiple ways they've dealt with the same things your going through, but theres one thing they forgot. A lot of times events in life you blame yourself for are beyond your control, you speak of bonds dissolving between you and friends. More likely than not this isn't your fault and is probably beyond the scope of your control. So what do you do? Life goes on. No matter how low you are in life, you'll always go back up. The only place to go from the bottom is the top. And if nothing else there's always chronic.
Anyway, hope everything goes well.