A life letter is a heartfelt message you write to someone when you're concerned that they may be thinking about suicide (or, that they may consider suicide in the future). For parents, it's a way to open up the conversation about suicide either because you're actively concerned, or because you want to be proactive.
Before we talk about what goes in the letter, let's talk about logistics. You're going to mark the letter with the person's name and put it in a
sealed envelope. When you give it to them, explain that they should save the letter and open it if they ever find themselves in a dark place where suicide starts to feel like an option.
They may never open it, or they may open it 5+ years down the road.
So the letter is not about what they're going through right now. It's about acknowledging that if they've opened the letter, they're very likely in a dark place, and you don't want them to be in that place alone. It's all about saying I'm here to help; let's get through this together. It is not about passing judgment on why the person feel this way. It's about acknowledging that life is hard, we all experience suffering, and there is hope.
One more tip: don't get caught up in having the perfect words. If the person is opening your letter in a moment of crisis, the exact words you say aren't going to matter. It's not intended to be the last thing you ever say, or to summarize all the advice you have. This should be a short, to-the-point letter that empowers the person to reach out for help when you might not otherwise know they need it.