I know a lot of people that were once suicidal, or who frequently battle suicidal feelings. And every time I talk to them when they are struggling, they ask me the same question "what do I have to live for?" I have to take a step back and think. What do you tell someone who has horrible circumstances, who thinks they have no other way out? If they don't see what they have to live for, how can you make them see? How can you see yourself?
I always come back to the same answer though. I tell them they have their future to live for. The future is never set in stone; every choice we make can change our future. When all hope seems to be gone, and they are tired of holding on, you are battling a suicidal person for THEIR life. And it's not an easy battle; it's an uphill battle; it's a battle that they will try their hardest to make you lose. And the only credit you get when and if you win that battle is the satisfaction of saving somebody's life.
I know it is hard to help a suicidal person, and if you start getting overwhelmed yourself, you should encourage them to talk to a professional. The most important thing to remember is that you are NOT responsible for a suicidal person's actions. In reality, you are not responsible for anyone else's actions. You can reach out a helping hand, and when they ask you what they have to live for, you can remind them that the future is never predetermined.