A note to my not-so-little boy

Dear Little Dog,
I can hardly believe I'm again writing you a birthday letter, but here we are celebrating your birthday.  Today my baby is five, and if I'm honest, you're not much of a baby. A big boy now, but so much your own boy. 
When I look at you I see a tall and lean little boy, bursting with his own distinct personality.  You can be silly and playful or you can brood with the best of them and it is always difficult to know which to expect.  Sometimes I wish I understood you better, I wish I could see inside and understand what makes you tick, but instead I'm left guessing trying to figure out your complexities.
Not always an easy year, but muddled through together.  We've waded through your frustration with your school, and though it isn't completely solved we do seem to be on the right track.  We've been swimming in the sea of sibling rivalry, and at the same time I watch you idolize your big brother, copying his every move.  I marvel as you choose to stay in his shadow more than you choose to spend time in the spotlight. I wonder when you'll tire of it and strike out on your own.
Your imagination is tremendous.  You are a pirate, a scientist, a super hero.  You love to dress up and pretend. When I asked your teachers what toys you like, they tell me you seem to prefer to make your own toys.  You live to create, to act and to explore.  And yet it isn't all clear sailing.  You are easily frustrated as your 5 year old body fails to live up to your expectations of what you should have mastered.  You carry a lot of "can't" with you when you could it only you'd try.  You befriend the troublemakers at school and get caught up in the wave of naughtiness.  It is hard for you to say no to someone you admire and I worry this will make things harder for you as you get older and adults become less understanding.
You are my little rock star, my tough guy, my badass.  You are also my snuggler, my worrier and my dreamer.  More than anything, you are mine.
Happy birthday, here's to another year of adventures and misadventures.

I love you, Little Dog.