Clara brought up a great example. There is a site that was created for Julie Whitt. The torch site.
The Torch - Index
Go there and read her blogs and story. It will truly inspire you to go on. She was an amazing woman and will continue to inspire people for years to come.
Stay strong. Find out what exercises you are doing that cause you the severe pain. Change them so they don't aggravate your back.. Speak to a back specialist and tell him what you are doing, what it results in and see if he can recommend exercises that won't cause the result you've been getting.. Don't give up, you will end up feeling much worse in the long run. Think of where you were before you started this. I am sure it was much worse then you are now. Don't give up, don't ever give up!