Everyone has a point in life like this, and you're not the first. What you need is someone that cares, and someone who wants to listen to you. Now this might not be the very best place to dscuss these kinds of things, but believe me, no matter how much you want to deny it, talking to someone who cares is the only medicine that completely works.
I've been in the situation myself, I've had friends in the same situation. (Not the exact death, smoking, drinking, little to do etc stuff per se, but the actual part where you wonder what meaning you have in life.)
Try to find someone who cares. Look for the light in the tunnel. People online aren't the ones you'll want to speak to about sensitive things like this, because they don't have the same kinds of feelings as if speaking to a real friend.
On the other hand, if you don't find anyone to talk to, you should try a shrink, or try to get out more. It might be tough to start with, but as long as you can find hope through all the darkness, you'll be way better off than reflecting on the negative.
Now I don't know you, and I probably never will, but I'm speaking of personal experience, and it's worked for more than half of the friends I've got today. Whatever you decide to do, I hope that you'll consider it. Just don't let yourself fall deeper in your thoughts. As soon as you start falling, it's a slim chance to get hold on solid ground again.