Question... About life in general? : /?

I'm 18 years old. I've been through a lot for someone my age, just putting that out there. Not trying to get sympathy or something. Honestly, I'm probably the most pessimistic person I've ever met. I'm so negative with EVERYTHING. I don't want to be that way though. I'm always wondering to myself, what's the point of life? I mean, we go to school for years, to get an education, to get a good career, to make money, so we can essentially live. But for what? By that time, our lives are already halfway over. I just over analyze alot I guess, but that's the way I always think. Unfortunately. I have been lately more than usual, because for some reason I've just been so angry and sad. Not sure why.. I just graduated hs, and going to college next fall, I thought I'd be excited, but I'm just worried. Also, my mom passed away about 3 months ago, so I'm not sure if this is contributing to how I'm feeling lately.. Advice anyone? : / Thank you.