I realize that you mean well, but your pat answer of “life is worth living” is kind of empty. The reason (as sad as it is) that many of us are on this site is because we DONâ€™T feel that way. One more cheery person telling us differently isn’t going to automatically change our minds.
I don’t want to discourage you from trying to dissuade people from taking their lives; actually, I applaud your desire to help. Maybe a better approach would be to ask why they feel the way they do. Many people in this situation are looking for empathy from those who understand, not just another person saying “don’t do it.” Being willing to listen & GENTLY encourage might be a better approach to effectively get your message across.