I'm always sad why is this?

It's likely because you're a teenager.

I'm not sure when it happened, but I was the same way. I was suicidal, I was miserable. I cut myself. I cried a lot. And then all of a sudden I just.. it's like a switch was flipped. I don't know if it's cause I'm not a teenager anymore (because you know, 20 is so far from being a teen), or my birth control changing hormones. Or perhaps even that I'm back in university and have a distraction, something put eat up my mental resources.

Try a hobby. Try talking to people. If you're female, try birth control, honestly.

Or gun through it.

But btw, this isn't philosophy.

I never liked it when people told me that conflict happens because "I'm a teenager." It's a little too helpless/fatalistic/just wait it out/useless advice. That being said, we do have to confess that there are impacts upon your emotions by biology; similarly, we can work with the variables of philosophy and self-understanding that we do have control over.

May I recommend reading Siddhartha as a start? I know that, reading it in high school, my mind was really blown away and brought to a better place. I've attached a quite synopsis/highlight of key concepts.

I had the same problem when I was a teenager but once I turned eighteen joined the military that sent me to war. Once you hear the rounds bursting around, you forget about all of your petty problems and only worry about how sleepy and hungry you are.

It looks there is a serious flaw in your present Time-Table. Get it rectified. Philosophize everything. Then only you can intuit properly.

Always means always - 24 hours in a day that too without sleep. I think you have some ill-conceived notion.

sounds like you have a hormonal imbalance, medicine will help that. some people have it and the 'chill' pill will re track it. you might want to talk to a dr. and see if he can get you something long enough to get it balanced again

it's natural to be sad and depressed in teen age. but don't let this destroy you. just find some reasons to be happy with, I am sure you will be able to find plenty.