Time Travel Dilemma
Let's suggest for a moment that you go out into space. Now, let time move on Earth faster than what you're experiencing because of relativity (I'm no physicist, so just imagine that's the scenario for now). What happens when you get back and you've barely aged, but Earth has moved forward 100 years?
Everyone has moved on and probably passed away, but there's been no "you" for quite some time. Maybe there are memories of you, but you have not affected any changes on Earth. Surely no one would presume you are dead because there's some record of the fact that you had left Earth 100 years ago, but are you 100 years older? You certainly don't look it!
What are the other implications of you returning? Everything else has changed, but you've essentially stayed the same. I imagine you'd go through some sort of post traumatic stress, separation anxiety, or SOMETHING!
In fact, I wonder whether people who consider suicide think about the world in this way. They can start to think about "the world without them," but I doubt it would appear this way to them. I think that's important to note though. The world just keep spinning without you. The only way you can make an impact is to keep living, while striving to make your mark. That's what we're all doing by living, in our own small and large ways.