Having battled depression so many times in my life, some of the coping strategies I have developed for myself may sound weird. But for me, they have worked, and perhaps they will work for you, too. You CAN survive this--it won't be easy nor will it be pretty, but you can!
#1: Try Something Creative
For me, involving myself in the active creation of something (usually a short story, piece of music, or website) helps me temporarily relieve the symptoms of depression. When I'm focused on building, shaping, editing, reworking, etc., my brain simply doesn't have time to notice the depression fog wrapping around it, and sometimes the fog even dissolves while I'm working. And when I'm finished with my project, the sense of accomplishment and pride in what I've been able to make helps ward off the nothingness, too, like lighting your way with a flashlight.
Over time, as I start and finish more and more projects, my brain gets "used" to the positive feelings of creation and completion. This means that when the nothingness tries to force its way back into my mind, it feels wrong and alien, and I can shake it off a little easier.
Here are a few ideas for creative things to help you retrain your thoughts:
#1b: Try Doing Creative Things With a Group
When possible, do your creative work alongside a group. This keeps you among people who are like-minded, who may be future friends and confidantes--you would be amazed how much that helps ward off depression. (See: my webdesign work among the community of designers at Amassment; my regular participation in my local Choral Society.) Even if actually talking to them feels impossible right now, at least lurking on forums or coming to a meeting or two can help you at least feel like you're not alone in doing whatever creative pursuit sets your heart aglow. Nothing is lonelier than feeling like you're doing your art in a void, and I would be the last person to suggest doing anything alone while you're depressed.
Human contact is one of the best antidotes to depression that I have ever found, even if it feels impossible to talk to others sometimes. Depression wants you to feel like nobody cares about you and it would be better if you died and got out of the way, but when you find a great supportive community, you can finally start battling back against that mindset.
#2: Keep Trying to Reach Out to People (Especially Friends and Family)
(related to my last point) I know this is HARD. Good LORD, it's hard sometimes, especially when your friends or family are dismissive of your depression or even berate you for it. But never stop looking for people who understand you. With the Internet and social media like it is today, there are many resources, forums, and support groups available to you, full of people just like us who have struggled and are still struggling with depression. Lurk on the forums for a while if you need to; learn all that you can about this disease that's eating your mind, and then speak about your experience to others. Make websites about it if you want to (that's what I did).
The more you talk about your depression and learn about how other people have survived, the less power it has over you. (Important note: if you have a bad experience with a depression forum or resource, drop it and move on to another one; ain't nobody got time for even MORE negativity!)
#3: Seek Out Professional Help
I know this sounds like the most trite advice ever, but if you've battled your depression alone for a long time and nothing seems to be getting better, PLEASE talk to a professional. Call a suicide hotline, reach out to your religious organization, talk to your doctor--do SOMETHING, or have someone call on your behalf. If you've tried every bit of advice on websites like this one and are just not finding anything to help, it's time to call in the big guns. There is no shame in getting help, and the people who would shame you for it should be ashamed of themselves for hindering someone else's recovery.
If cost is the biggest barrier to getting help, here are several ways to save on treatment costs, such as seeking out free self-help groups in your community, pill splitting, etc.
Remember, depression is the enemy, and you are a warrior!