Great poem.  It's the truth, totally.  People need to stop whining about everything.  But it's not only teenagers who whine.  Adults do too.  Anyways, bye.

Someone once taught me that it doesn't matter what other people think of you as long as you like yourself.  That's what I live by.

"Your anger is a gift"-Rage Against The Machine
"Only God can judge me" Tupac Shakur

Finally someone agrees with me on something!
I asked my uncle what he does (he works at a computer company thing) and he said that he listens to adults whine to him about their every little problem.  I told him that he should just say to them "I'm not paid to listen to you whine, that's not why I came to work here" or something.  I only whine when I want something really really bad and it can't wait.  Or if I need to go somewhere, since I can't drive yet.  But a lot of adults I know can get whatever they want and can drive, so I dunno waht their problem is.

Someone once taught me that it doesn't matter what other people think of you as long as you like yourself.  That's what I live by.

Ditto to everyone else.  
BUT! I liked the way you wrote this.
Very well done.  

You wouldn't worry about what people thought about you if you knew how seldom they did.