Believe me, I understand.
I've stood at that ledge wishing I had the courage to end everything. My little brother was the only thing that gave me the strength to continue fighting. I couldn't leave him.
My advice though..obviously don't do it. Fight it as much as you can.
But, I also think you need to really look at your life. If you died, what would happen? Look at your family, your friends, how would they react? The thing I really think you should do is to find something, anything that means alot to you. And keep living simply because of it. Find a family member, a friend, a pet, an object, a goal in life..anything and hold onto it as tightly as you can. Don't ever let go.
If you feel it's helpless, that there's nothing out there..hold on to VT. I can tell you now, if you weren't here it would affect alot of us here, alot of people care for you here. Just look at Cosmos' post, alot of us feel the same way, I know I do.
Hang in there.