I know this may come as a surprise to you, but I was your age once too. I know, I know... you can pick yourself off of the floor now. I'll wait. (cricket. cricket. cricket) OK, where were we. Oh yes. A funny thing happens when you get to be old like I am. It's something I like to call the wisdom of years. What that means is that having lived through an awful lot, I have a wisdom that you don't have yet. I am able to look at a situation, and based on past experiences, know how it's going to turn out in the end and act accordingly.
I was also 12 once. And I see that you look at a situation, and based on your limited life experiences, and jump right in without any thought to the outcome or consequences. If there is one thing I can hope to teach you before you leave for the great bit unknown, it's to stop and think before you act.
Try not to be so impulsive. Sometimes being very smart is a bit of a curse. With great intelligence comes limited social skills and common sense. No one is a greater testament to this than you. I have seen you in action, and I sometimes have to sit back and shake my head. Those jokes that only your teacher gets and laughs at... sometimes hurt your friends feelings because they don't have the intelligence to comprehend your humor and they think you are making fun of them.
What I have also seen this past year however, is a nicer relationship with your sister. I know she's younger, and you consider her "pesky"... but she really does love and admire you. I see you guys doing more things together lately. As rough as it is on my ears, I love it when you take out your instruments and practice together. That you do it all on your own and I don't have to nag makes it all that much better. I see you asking her to play games, and agreeing to do things when she asks. And I have to tell you it makes my heart happy. She is the greatest treasure you will have when you are older. Take care of her. Protect her. Be a good example. And don't be afraid to tell her that you love her. It's OK. I won't tell your friends.
Happy Birthday (belated) Mr. Man. I hope this next year is wonderful for you. Try not to let those hormones get you down too much, and I'll try not to nag you too much about the clothes always being on the floor.
(ps. you shouldn't slouch so much while you use the computer)