You don't give up because there is still a part of you that wants to fight. Given your quote, you must have faith. Sometimes we have to wade through some pretty hard times for reasons that are currently beyond our understanding. Are you familiar with the serenity prayer?

God, grant me the serenity to accept the things I cannot change
Courage to change the things i can
And the wisdom to know the difference

All we can do is try to support eachother, and when needed, seek professional advice. That doesn't offer much comfort, and its easy to feel alone, no matter how many people are in your life. Hang on though. You never know when things may change, or what experience you are getting from your trip through the darkness.

Sam2