This is a really great question, I would value the life of others because we are humans and we were built to communicate, now there's one thing...
If you have questioned your very existence and what is there to do with life, about what does being alive mean,
You'll probably end up with the conclusion that one's life is complete irrelevant, for what ONLY matters on the bigger picture is survival of the specie (say humans)

I mean right now you are already neglecting thousands if not millions of people dying around the globe. You are only affected is someone you know dies.