Allow me to be existential for a moment

I had a really late night yesterday. This is normal. I get home, work until the early hours, and doze off during the night before waking up three hours later to repeat. Almost every day of my life for the past three years has been more or less the same. It will continue to be the same for years to come. I struggle with finding purpose here, and I'm getting impatient. All I see in my future is years of school, on the same sleep schedule I have now, then working a job I hate, getting married and having kids that keep me up all night, and wondering what my purpose is.

If this is all there is for me, then why am I still alive? Why does my brain think it's important to live when I know that I'm not going to contribute to anything big? What I do won't matter to anyone, so why should it matter to me?

You don't need to answer, I just wanted to vent for no reason at all.

I suppose what I'm trying to convey is that if that's all there is for me, I've already done it. If my purpose it to nearly collapse of exhaustion and undernourishment every day and work until my face hits the desk at 3:30 AM, then that's it. If that's all I will be doing for the rest of my life, why should I attempt to see the end of it?
(Believe me, I'm not trying to put you down, I just have a lot to ramble on about)

Well for me… I've found the answer in Christ. When you are a child of God, your purpose becomes actually defined, your worth is actually defined, and it's all a truth that's outside of yourself and everyone else and can never be altered. And it all means something, it means so much that it's bigger than the universe itself. I might sound super basic or cheesy, but it's what I believe and I'd love to tell you more about it if you want me to. I won't be mad if you don't want to hear it, though. :P